The Supreme Court is to rule tomorrow whether law firms should be historically liable for claims they failed to advise former clients to pursue. In Perry v Raleys Solicitors justices will resolve whether the disgruntled client must prove their claim was valid.

Almost two years ago, the Court of Appeal said the defunct Yorkshire firm, which went into administration in 2016, should pay almost £15,000 for negligent advice to retired miner Frank Perry. Raleys had secured a settlement in 1999 for Perry’s injury for hand-arm vibration syndrome, but launched a claim against the firm alleging his case had been under-settled.

Leeds County Court ruled that Raleys’ admitted negligence had not affected Perry’s prospects of succeeding on this element of the claim.

On appeal, Lady Justice Gloster said the judge had conducted a ‘trial within a trial’ and said it was ‘intellectually unsound’ to require the court to investigate whether a claimant could prove what he would have done many years earlier. She ruled that the trial judge had found incorrectly that Perry was ineligible to pursue the extra claim.

In its explanation of the case, the Supreme Court says the issue is whether a claimant must prove, on the balance of probabilities, that the former missed claim would have been an honest one. Justices will also decide in what circumstances an appeal court should interfere with a trial judge’s findings of fact.

The Supreme Court heard the Raleys appeal in November, and judgment will be given by Lady Hale, Lord Wilson, Lord Hodge, Lord Lloyd-Jones and Lord Briggs.