Belfast firms McCartan Turkington Breen (MTB) and Edwards & Co Solicitors represented separate groups of PSNI officers and civilian staff in the appeal.

The PSNI had previously accepted that the manner in which they calculated holiday pay was incorrect, but brought an appeal to challenge how far back the claims could reach and the correct method of calculating the underpayments.

The appeal centred in part on the precise meaning of a “series of deductions or payments” in the Employment Rights (Northern Ireland) Order 1996. The court said the PSNI’s narrower interpretation would allow a “canny operator to game the system” by spacing out payments over a longer period.

It is now up to the Industrial Tribunal in Belfast to decide how much each PSNI employee affected by the underpayments issue should receive.

Niall McMullan, partner and head of employment law at Edwards & Co, welcomed the “resounding and emphatic outcome” for his clients, who were supported by the Police Federation for Northern Ireland.

Mr McMullan said: “Naturally, our clients are delighted by this outcome. They will get what they are entitled to under the law and it confirms that police officers also have the same redress as other workers in Northern Ireland when it comes to calculation of holiday pay.

“The Industrial Tribunal phase could take some considerable time to process. Clients however will take comfort today from knowing they have been successful once more.”

McCartan Turkington Breen said: “We are delighted by the outcome for our PSNI clients following this morning’s Supreme Court judgment.”