In the case of Chweidan v Mischon de Reya [2014] EWHC 2685 (QB), the court considered the issue of quantifying loss of chance. The court gave useful guidance on how loss is quantified in loss of chance cases. The claimant was awarded 18% of his losses claimed on the basis that his prospects of success were 18%.    


The case involved a former bank employee who alleged discrimination against his employers following an injury sustained during a skiing trip. The claimant was successful at an employment tribunal and was awarded £500,000. The defendant lodged an appeal. The claimant sought to lodge a cross-appeal but his solicitors failed to lodge the cross-appeal in time. As a result of the failure to lodge the cross-appeal, the claimant’s award was reduced to £68,000 and with a costs bill in excess of the monies awarded.

The claimant sought recovery from his solicitors on the basis that he had suffered from a loss of chance in respect of the failure to lodge the cross-appeal.

The solicitors admitted the breach but argued that the claimant’s cross-appeal had so little chance of success that he had not suffered a loss.


The court held that the prospects of the cross appeal succeeding were 18% and the claimant’s employer may have settled. The claimant was awarded 18% of the losses claimed.

The court gave general guidance on how the loss should be quantified in loss of chance cases. Quantification should be a mathematical calculation based on multiplying the various different hurdles that a claimant must overcome to be successful in a loss of chance case. The process to consider is as follows:

  • There must be more than negligible prospects of success
  • The court should make a realistic appraisal of the claimant’s prospects should the litigation conclude at trial
  • The court should assess the likely level of damages the claimant would probably have received (with an appropriate fraction applied for the uncertainties of litigation)
  • The level of detail in which this assessment is made will depend on the nature of the case (sometimes broad brush and sometimes in more detail)
  • The court should account for the possibility that the matter would have settled before trial and must remember that the oral and written evidence would be more limited than that available at trial
  • If there are separate hurdles for the claimant to overcome, the court should multiply the prospects together to give an overall percentage prospect of success.    


This case is relevant where an existing professional negligence claim has been unsuccessful as a result of the later negligence of the solicitors instructed to prosecute the claim.

Any claim of loss of chance in professional negligence results in the unusual occurrence of solicitors playing down the prospects of their former client’s claims.

The court’s guidance in this matter gives greater transparency in how losses in these claims will be assessed.

It is arguable that the burden of proof is reduced for these cases (from the standard balance of probabilities i.e. over 50%).