In North Cumbria University Hospitals NHS Trust v Fox and others (formerly known as North Cumbria Acute Hospitals NHS Trust v Potter and others) the Court of Appeal held that the claimants' applications to add new comparators to their equal pay claims, which represented a new cause of action, had been presented in time. The Court of Appeal reached its decision on the basis of a new point raised by the claimants, namely that theirs were "stable employment" cases.

The Court of Appeal approved the decision in Slack and others v Cumbria County Council and found it unnecessary to resolve the differences between the tribunal and the EAT in the current proceedings. Identifying a stable employment relationship involves applying a broad, non-technical test which assesses the character of the work and the employment relationship in practical terms. In this context, the word "employment" is intended to refer to the nature of the work, rather than the legal terms under which it is carried out.