In Dufoo -v- Tolaini and Ors [2014] EWCA Civ 1536 the Court of Appeal considered the issue of costs liability between the claimants where two claimants had settled their action with a defendant but a third went on to trial and lost. It was held that, despite an agreement that the defendant would no...
So, get the defendant to indemnify you against this risk as part of your settlement agreement with the defendant. The annoyed claimant may be able to construct a loss of chance claim against his solicitors for failing to seek to do that (assuming they did not seek to do it).