The judgment of HHJ Mithani QC in Colar v Highways England Company Ltd [2019] EW Misc 17 (CC) has recently arrived on BAILLI.  It provides an illustration of the danger of defending a claim “at all costs”.  The judge was critical of the defendant’s disclosure, a failure to call key and obvious evidence and the conduct of the defendant’s expert witness.


“A hugely unsatisfactory feature of the defence of this claim by the Defendant is that it has sought to defend this claim at all cost. It has taken every conceivable point available to it in its defence of the claim and has failed in its duty to provide proper disclosure to the Claimants of documents which are material to this case.”


The claimants were injured when a tree fell from a central reservation onto a car in which they were travelling.   An action was issued against the defendant highway authority alleging that it was negligent in failing to inspect the tree and notice it was diseased. The defendant denied liability.  The judge found for the claimant.



40 A hugely unsatisfactory feature of the defence of this claim by the Defendant is that it has sought to defend this claim at all cost. It has taken every conceivable point available to it in its defence of the claim and has failed in its duty to provide proper disclosure to the Claimants of documents which are material to this case.
41 As a public authority, I would expect the Defendant to present to the court a balanced view of the evidence with a view to the court deciding whether the claim against it is made out. That – what I call a duty to act fairly against the Claimants – means that the Defendant should supply all the material which may be relevant in this case to the Claimants and not seek to pick and choose what material it should make available to them. It also means that if it is possible for it to call a witness (such as Ms Ellen Tune) who may be in a position to give relevant evidence to the court, it should, at least, make information (such as the contact details of the witness) relating to that evidence available to the Claimants because the Claimants’ solicitors are not readily likely to have that information available to them, though, in the present case, the Claimants’ solicitors do not appear to have made any enquiries themselves about Ms Tune (until after the adjournment I granted to enable proper disclosure to be given by the Defendant to the Claimants) when it might have been possible (and was) without much effort to trace her.
42 When I enquired why Ms Tune had not provided any written evidence, I was informed that even if she were called, she is unlikely to remember anything about the inspection which she carried out and that, in any event, efforts made to trace her had proved to be fruitless.
43 I do not consider either point to have any substance.


The judge had some criticisms of the defendant’s expert.

The questions which Mr Pennock asked were perfectly straightforward. He wished to know whether the standards applied by the Defendant complied with the standards expected from highway authorities, and others, whose management of a soft estate could expose members of the public to the risk of injury. He wished to obtain Mr Forbes-Laird’s views about whether the Defendant had taken all reasonable and practicable steps to make the public safe by reference to the observations made in Witley Parish Council and Stagecoach. Mr Forbes-Laird’s evidence was completely unhelpful about whether the Defendant complied with those standards. He seemed throughout simply to be advancing the Defendant’s case.
94          I am unable to accept that the images show the Tree as having been pruned in the purported 2012 inspection. That is because, there was, as I have found, no such inspection. Nor am I able to find that it was pruned subsequently (i.e. after the alleged 2012 inspection but before it fell), though I do not believe that it was ever suggested that it had been. The opinion given by Mr Forbes-Laird was based purely on his interpretation of the Bing images and the information contained in the tree-inspection records prepared by Ms Tune. Even on Mr Forbes-Laird’s analysis, there were at least three principal reasons for the presentation of the Tree in that state in the Bing images, something which he accepts in paragraph 2.2.3 of his addendum report, although he states in paragraph 2.2.5 that the pruning of the Tree was the most likely explanation. However, I consider that the alleged pruning of the Tree is the least likely of the possible causes of the presentation of the Tree in the Bing images. There is nothing in the tree-inspection records prepared by Ms Tune about the Tree, so that source of information is of little assistance in determining what Ms Tune saw when she undertook her inspection. There may be features of the presentation of the Tree which show signs of pruning but to conclude, as Mr Forbes-Laird did, that this was the most likely explanation is to proceed on the basis that the Tree was pruned in 2012, which I have found simply could not have been the case. It is almost impossible for me to see how Mr Forbes-Laird could have come to that conclusion based on the presentation of the Tree in the Bing images only.
95          I also found that, rather than give true expert evidence on the point, Mr Forbes-Laird appeared primarily to be advancing the Defendant’s case – or as Mr Murray accused Mr Benzies of doing on behalf of the Claimants – acting as counsel for the Defendant. Whether or not Mr Benzies appreciated his true duties as an expert when he signed his original report, the fact is that, in the course of giving oral evidence, it was Mr Forbes-Laird who did not appreciate his proper functions when presenting his expert evidence to the court. Although discarding the proposition that the Tree was “unlikely” to be infected with K. Deusta at paragraph 2.2.5 of his addendum report, he was quite prepared to go much further saying that it was “highly unlikely” [9] or “highly improbable” [10] that it was. His opinion, as the following exchange demonstrates (my underlined emphasis), was premised on the basis that it was clear to him from the evidence which he had heard that there had been an inspection of the Tree in 2012 [11]:
“Q.       If this tree had been pruned, say, the previous year, and one knows from the other evidence that there was a tree inspection regime in 2012 —
MR PENNOCK:  Well, again —
JUDGE MITHANI:  I will make my findings in relation to that.”
Similarly, later on [12], there is the following exchange between Mr Forbes-Laird and Mr Pennock (again my underlined emphasis):
“Q.       Walking?  As far as we know, she was driven past at 50 miles an hour, Mr Forbes-Laird; what do you say now in relation to that?
  1. I say that I was in court when Miss Brookes gave her evidence, and I heard her say that the evidence from the inspection record identifies the inspector to have been present on the ground, either side of the tree, and in all probability walked past it. Is it possible she drove past it?  I suppose so, but do we know this?  We do not.  But Miss Brookes gave evidence, and we heard it.
  2. That is not your area of expert evidence, and I will not go into with it you, and just —
  3. Well, I’m sorry, it is my area of expert evidence, because I functioned as a highway tree inspector for three years.
  4. Your Honour, I’m putting a marker down: I’m not going to challenge him on this;it’s not his area of expert evidence; he’s acting as an advocate now, rather than an expert witness.
  5. I’m not; I simply heard what Miss Brookes said in court.
  6. If you’re not an expert on it, it’s a matter for the judge to weigh up the evidence, Mr Forbes-Laird, not for you to make submissions on behalf of the defendant; I would ask you to remember that.  Now, we have the tree presenting in March 2013 with signs and symptoms, one of the possibilities of which is disease; why should an inspector ignore that?”
I agree wholly with Mr Pennock. It was no part of Mr Forbes-Laird’s function as an expert to trespass into the territory of the judge by accepting, for the purpose of presenting his expert evidence, that the account of a witness had to be correct. It is not that he did not know that Mrs Brookes’ account was subject to serious challenge. He did and, in the event, I have found it to be largely unreliable. He should have presented his evidence on the likely scenarios based on the rival positions advanced by the parties, leaving it to the court to determine any factual issues which arose. He might legitimately have said that the most likely explanation of the presentation of the Tree in the Bing images was that it had been pruned and that it was likely to have been pruned at some stage before the date of the Bing images in March 2013. However, to accept as a fact that the pruning took place in 2012, was not for him to say. 
96          I can largely discard the possibility that the Tree was affected by roadside poisoning due to the use of de-icing salt used on roads. This premise is based entirely, or largely, on speculation. There is no evidence whatsoever to support this proposition. Mr Benzies’ evidence on this point (as regards whether he had thought about this issue in his reports) was, as Mr Murray points out in paragraphs 59 and 60 of his skeleton argument, unsatisfactory because he appeared to suggest that he had considered the point and had not realised that it had not been included in his report. However, I am unable to accept that it undermined the substance of the evidence summarised in his addendum report. I wholly agree with Mr Benzies that there would have to be a substantial amount of salt needed to cause damage to a tree in the way Mr Forbes-Laird contended, and it has to be questioned why this tree (i.e. the Tree) was affected when there is no evidence of other, nearby trees, being similarly affected. On the substantive issue of the likelihood of this, I cannot disagree with what Mr Benzies had to say [13]:
“A:       Are you saying – is it superficial salt damage due to spray, burning of the leaves and causing minute dieback, or are you talking about large amounts of salt in the soil over time?
  1. I’m talking about considerable amounts of salt that are causing – go through to the roots, and are a possibility for causing a tree to exhibit signs of ill health, and then, when the de-icing salt stops, the tree can recover.  This is well-known; I don’t think I’m saying anything radical in terms of arboricultural —
  2. I would say that there has to be an awful lot of salt in order to cause those symptoms.  The type of – amount of salt that you’re talking about is a large dump in the vicinity of the tree; something that does happen, but I would suggest is implausible in a central reservation of the A45, to be used as a salt store for de-icing.
  3. Well, I’m sure that Mr Forbes-Laird will be able to take the court through how that will work, but I suggest to you that that was another option that your report simply failed to consider?”
97          Mr Forbes-Laird’s evidence on that point, in his addendum report, was only brief – see paragraph 2.3.5 of his addendum report – and there is no reference to this point in the conclusions contained in his original report – though he did deal with the point in his oral evidence, both when he first gave evidence and also when he was recalled. But both this reason, and the possibility that the Tree was affected by drought, were based on speculation. Mr Forbes-Laird might have thought of a host of other, speculative, possibilities about how the Tree presented itself in the Bing images. But he seemed easily to discard the one possibility which it must have been obvious to any expert about the presentation of the Tree – that it was infected with some type of fungal disease which needed investigation.
98          Just as McKay J found in Bowen that his confidence in Mr Forbes-Laird as an expert in that case was diminished because Mr Forbes-Laird could not present his expert evidence in a dispassionate manner, I come to the same conclusion about him in this case. He seemed, at every possible point, to be advancing the case of the Defendant before me and had lost all sense of what his true functions were. His evidence was not impartial. He was very careful in the words he chose when giving evidence, and sounded very impressive when he did so. However, he was not prepared to give answers to straightforward questions which were put to him.
99          I asked Mr Forbes-Laird that given, on his hypothesis, Ms Tune would not have discovered the signs of K. Deusta, when she conducted her inspection nine months before the Tree fell, was there a point in time when she might have been able to identify, at least, the sign of disease that caused her to raise an enquiry about the state of the Tree and about how to deal with it if it was found on subsequent enquiry to be diseased. He refused to provide any, or any meaningful, response to that question. The following excerpt of my exchanges with him demonstrates this (my underlined emphasis) [14]:
                                “Q.       Right, let’s stick with the point that I’m – we’re trying to get out of you.  That immediately before this tree fell, right, if you were to stick a probe into the base of the tree or one of the major roots coming off it, you will have discovered, on the balance of probabilities, rotten wood, wouldn’t you?
  1. I can’t say.  Some way below ground one might have found it.
JUDGE MITHANI:  Take it back – just help the witness please, I – I – when would your probe have – let’s put it this way – perhaps work backwards.  When would your probe – at what stage before the tree fell would your probe have discovered that there was something amiss?  How – when would you say, six months before it fell, nine months before?  Because you seem to be so clear that it’s highly unlikely —
  1. I can see – your Honour, I can see from the photographs that some of the below ground parts of the tree are soft.
  2. Yes.
  3. If I had, before the tree fell, been able to get my steel rod deep enough below ground to poke those parts of the tree —
  4. Yes.
  5. I would have found soft wood.
  6. And when would that have been?
  7. That would have been, I’m guessing, a year perhaps before the tree fell, maybe, but it is – it is a guess and that as I say, would have required a relatively lucky strike —
  8. Ok, right, let’s – let’s – let’s —
  9. — and it would have required me to be able to probe below ground.
  10. Let – let, please, it’s very important that we find this out because there is a wide spectrum of ifs and buts.  We know the tree fell in 2013.
  11. Yes.
  12. We know that your evidence is that the time when it was inspected, it is like – unlikely to have shown signs by the use of a probe which suggested that something was drastically wrong with it, so we know that.  That’s your evidence, as I understand it.  Now, what I’m asking you is at what stage between that first two dates, the February 2000 and – the 2013 inspection and the date when the tree fell.  Would you be able to turn round and say to me, because I’m relying on your expert evidence and say, “Well, three months before the tree fell, if I’d actually have put a probe in, you know, hurrah, or – or worse,” I mean, obviously —
  13. Yes, I – I – I understand, I understand —
  14. — that’s what I – I mean, I – I —
  15. — I understand precisely the case.
  16. I just want you to tell me that, please.
  17. So —
                        MR MURRAY:   I need to —
                        JUDGE MITHANI:  When, on a balance of probabilities —
  1. Yes.
  2. — would you say?
                        MR MURRAY:   And you said a year.
  1. So, if I may answer the judge’s question.
                        JUDGE MITHANI:  Sure – sure, absolutely, Mr – Mr Pennock, I interrupted.
  1. It has been put to me, this concept of probing through the soil to the base of the tree which really is not something that I would do or – or find efficacious.  If I was concerned about root disease, your Honour, I would have got out the trowel that I carry in my bag and I would have dug around the base of the tree to try and dig down to the main structural roots, perhaps going down below ground a foot or so, to see if I could find indications of – of decay.
  2. Ok, when would you do that?
  3. And – and I would do that if I felt that there were visual inspection of the tree gave me cause for concern.
  4. Well, I note all that and I – and I hope I’m not asking a question that’s daft because I’m prone to and I apologise in advance if I am and I’ll be stopped if I’m asking too many questions but I do need to get this round my head properly.  What inspection, and when carried out, would enable you to say, “There is something wrong here.”  We know that you say it wouldn’t have been at the last inspection before the tree fell, would it be days before the tree fell, hours before the tree fell, months before the tree fell?  That’s all I want to know.
  5. I would have expected to be able to find decay by digging round the base of the tree within six months, minimum, maybe as long as 18 months, possibly even two years, but that would require digging down amongst the roots of some of the tree.
  6.  When would it have been possible for you to have been able to do it without being lucky, as you put it, in a – it looks a bit – it looks a bit awkward and there you are.  That’s what I’m asking, would it have been three months before?
  7. I don’t know I would have found it at all with a probe.
  8. Right.
  9. But my – my modus operandum would have been in that case, to – to dig and by digging down, I would probably have found the decay.
  10. (Inaudible).
  11. Six, eight – 18 months, something like that, maybe two years.”
100      I pause there. The question I was attempting to obtain an answer to from Mr Forbes-Laird was when an inspector would have been put on enquiry that there was something wrong with a tree such as to make it appropriate for further enquiries and investigations to be conducted in relation to it. In the course of those exchanges, Mr Forbes-Laird said:
      “I don’t know I would have found it at all with a probe.”
101      I presume he meant to say “without a probe”. I am unable to accept what Mr Forbes-Laird had to say because it is inconsistent with what he had to say when he was recalled to give evidence. But even if he is right about that, it would be an unacceptable risk to expose the public to the risk of a falling tree when it was not possible on a visual inspection to know until it actually fell (i.e. not to know at any time before it fell) that it might be infected with a disease which may cause it to fall, particularly if it is a disease which is as common as K. Deusta, i.e. the third most common wood-decay fungus associated with structural failure.
102      Mr Forbes-Laird was asked on a number of occasions when he was recalled about whether, if the Tree had not been pruned in 2012, it would have been possible without a significant amount of difficulty to ascertain if it was infected with a fungal disease. Mr Forbes-Laird reluctantly admitted that it would have been possible to do so (but not without a great amount of pushing and probing from Mr Pennock, as the exchanges at page 36 et seq of the transcript of the proceedings on 9 July 2019 demonstrate):
“Q.       The phrase is “reasonable care”, Mr Forbes-Laird.  Mr Benzies is of the opinion that this tree, in March 2013, showed signs of disease; you do not disagree with him: you say, “That’s potentially correct, however I think it may be pruning”.  Now, “reasonable care” in this very high-risk area would’ve involved a further investigation of this tree, having seen it present in this fashion, potentially diseased: she ought to have dismounted from the car, gone to the tree, removed the epicormic growth if one could, but dug down with her trowel, as you say, and she’d have found the disease, wouldn’t she?
  1. If that invasive or semi-invasive below-ground investigation had been undertaken, I think the disease would probably have been found.
  2. Thank you.”
Then at page 44 of that transcript:
“Q.       Now, in relation to the 2009 photographs, you said, “I would not have signed the tree off in 2009 without further investigation”.  Based on that photograph alone from March 2013, you wouldn’t sign that off as safe and healthy without further investigation, would you?
  1. No, and that is precisely the terminology that I used in 2009 when I was looking at the photograph.  But, because my evidence is that what I see in the 2013 photographs looks more like a tree that has been pruned than anything else, if that is what I found on the ground, I would have no further concerns.
  2. And if it was not what you found on the ground and you didn’t see signs of pruning?
  3. Then I would have regard for two factors: where the tree is and whether there are explanations for its condition, what those explanations are, and I would then respond accordingly.  If I had seen that on the ground, and if I had seen the tree had not been pruned, I might well have said it needed further investigation.”
103      It almost goes without saying that even on Mr Forbes-Laird’s analysis, if, as I find, there was no pruning of the Tree in 2012, and no de-icing poisoning or drought, then Ms Tune should have identified from the state of the presentation of the Tree when she inspected it on 19 February 2013 that it needed looking into to ascertain whether it was diseased and what should have been done about it. So far as he suggests otherwise, I reject what he says.
104      It is right that I deal briefly with another point which Mr Forbes-Laird mentioned in his evidence. He stated that dead wood would only drop from the crown of the tree on a significant scale if the tree’s vascular system had been fundamentally compromised, whereas only approximately 5% of the Tree’s vascular system had been affected by K. Deusta. As he said in his addendum report:
“My final observation on Mr Benzies’ images is that if they show the tree in a poor condition due to the disease, this would have only resulted from invasion of the outermost annual rings by the fungus. As I explained during oral evidence with reference to the stem cross sectional photograph, marked up by me to show the extent of vascular dysfunction, it is clear that the area of hydraulically active tissue lost to the disease is of the order of 5% of the whole.  In no way could this account for crown‐wide dieback of the sort promoted by Mr Benzies: quite simply, the required mechanism is not apparent in the evidence.”
105      I am unable to accept that this conclusion is obvious, or even likely, from the photograph of the base of the Tree which was inspected by Mr Benzies on 8 April 2014. The photograph shows a very substantial area of the tree to be affected – the suggestion that it was 40% was not disputed by Mr Forbes-Laird. How Mr Forbes-Laird can deduce from this photograph alone that only 5% of the active tissue lost could be attributed to the disease is quite beyond my comprehension. But the important point here is this: if, as I have found, this is the manner in which the Tree presented itself on 19 February 2013, and that it could not be down to pruning or poisoning, it does not take any great amount of ingenuity to work out that it could only be down to disease.
106      I am unable to accept the criticisms made by Mr Murray about the addendum report of Mr Benzies and the oral evidence he gave when he was recalled to give evidence. Whether or not he had appreciated the significance of the declarations which should have been included in his original report, he did his best to assist the court. It is alleged by Mr Murray that Mr Benzies was indulging in speculation. I do not consider that he was. He was asked questions by Mr Murray which involved speculating about the Defendant’s case (in relation to all three matters which Mr Forbes-Laird indicated were the likely cause of the presentation of the Tree, i.e. pruning, poisoning due to the use of de-icing salt and drought) and he gave answers based on what he was asked. If that may have involved his providing answers which amounted to speculation, it was because he was asked questions which were speculative in nature. Mr Forbes-Laird, on the other hand, refused to answer, or to answer satisfactorily, any question which could undermine the Defendant’s case. As regards the failure of Mr Benzies to include the expert’s declarations in his original report, I accepted the submission of the Claimants that this was not deliberate and gave permission to the Claimants to rely on that report and he gave his evidence after having been sworn to the contents of those declarations.
107      Just as the Defendant’s position on breach of duty lacks substance, its position on the issue of causation also lacks substance. It amounts to saying little more than this: “although there is no documentary evidence at all that the Tree was pruned, it was. If it was not pruned, it was subject to de-icing or drought. That is because Mr Forbes-Laird (who provided better expert evidence than Mr Benzies) says so.” That position proceeds on a basis which is fundamentally flawed: it is clear from the evidence that the Tree was not pruned, and the de-icing and drought are matters of pure conjecture. Mr Forbes-Laird might have thought of a host of other matters, amounting to speculation, which could have affected the Tree. The plain fact is that I found much of his evidence to be unreliable, not only because it proceeded on assumptions which it was not appropriate for him to make but also because his evidence was largely partisan and biased. He appeared to be intent throughout on supporting the Defendant’s extremely weak case on causation.
108      I come to the resounding conclusion that the most probable cause of the presentation of the Tree in the Bing images was due to K. Deusta. I would not have expected Ms Tune to know that from a properly-conducted visual inspection of the Tree. However, the presentation of the Tree should have put her on enquiry that there was something wrong with it and that the matter needed further investigation. She did not take any steps to enable such an investigation to be conducted.
109      I, therefore, find causation to be established.