[1] She typically had deployments of 5-8 years in support of the Trafalgar-class submarine on duty east of Suez, with a secondary role as a mothership for British and US minesweepers in the Persian Gulf.

Diligence was the Royal Navy's primary battle damage repair unit, and was on short notice to react to developing situations worldwide.

She first served the Royal Fleet Auxiliary (RFA) immediately after the Falklands War as a civilian owned ship taken up from the trade (STUFT).

At the end of the Iran–Iraq War, the Straits of Hormuz were mined, and Diligence supported the multinational minesweeping operation to clear that vital chokepoint.

In 1995, according to British reports, Diligence was confronted and illuminated by the radar of the Argentine corvette ARA Granville, which was harassing shipping near the Falklands.

Her accommodation areas, galley and engine room were all upgraded, with the intention of extending the ship's service life until the middle of the next decade.

A £17.6m refit was carried out from June 2012 to February 2013[7] ahead of a deployment to the Mediterranean and Gulf region in support of the COUGAR 13 task group.

A Royal Navy spokesman told IHS Jane's that Diligence was considered to be "an aged singleton ship with increasing obsolescence issues", and that it was no longer cost-effective to maintain her in service.

In April 2023, it was revealed that the ship was to be scrapped after no suitable buyers materialised,[11] and in March 2024 she departed the UK for the final time, under tow to a scrapyard in Turkey.