## Facts

- The claimant alleged that Raleys Solicitors negligently failed to advise him about a potential claim for services rendered during his employment.
- The claimant argued that if he had been properly advised, he would have pursued a compensation claim and obtained a financial benefit.
- The evidence presented by the claimant was determined by the court to be insufficient to establish a real and substantial chance of securing compensation, as it lacked necessary factual and evidential support.

## Issues

1. Whether the claimant had to prove, on the balance of probabilities, that the lost opportunity was real and substantial rather than merely speculative.
2. Whether the claimant had provided sufficient evidence to demonstrate both the existence and value of the lost opportunity.
3. Whether causation and quantification should be kept distinct when assessing lost chance claims in professional negligence cases.

## Decision

- The Supreme Court held that claimants in loss of chance professional negligence claims must present robust evidence showing the lost opportunity had a real and substantial value.
- The Court found that the claimant’s assertions in this case were speculative and unsupported by adequate evidence.
- The Court reaffirmed that causation and quantification are distinct elements in such claims; claimants must first prove the breach caused the loss of a real opportunity before quantifying its value.
- The claimant’s failure to establish the existence of a real and substantial lost chance meant the claim did not succeed.

## Legal Principles

- The doctrine of lost chance allows for recovery of damages for missed opportunities, but only if the lost chance is real, substantial, and not speculative.
- The burden is on the claimant to prove, on the balance of probabilities, both that they would have taken the necessary steps to pursue the opportunity and that those steps had a real prospect of a favorable outcome.
- There is a clear distinction between the requirement to prove causation (that negligence caused a lost chance) and the process of quantification (valuing the lost chance once established).
- Reference was made to principles in Allied Maples Group Ltd v Simmons & Simmons [1995] 1 WLR 1602 regarding assessment of lost chance claims.

## Conclusion

The Supreme Court’s decision in Perry v Raleys Solicitors [2019] UKSC 5 underlines the high evidentiary standard required from claimants in lost chance professional negligence cases, mandating proof that a missed opportunity was real and substantial, and decisively distinguishing between causation and quantification in such claims.
