She was on a long-term charter from 1967 to support the Royal Navy east of Suez and was at the time the largest ship in the RFA fleet.

Derwentdale had no replenishment at sea (RAS) equipment and was later classed as a Mobile Reserve Tanker.

On 23 November 1967 she sailed to Tyneside for these modifications by Swan Hunter (Dry Docks) Ltd, Wallsend, was renamed Derwentdale and became the largest ever ship in the RFA.

[1] On 17 June 1967 Halcyon Breeze was chartered by the Admiralty and two days later became the first of the Dale class to be formally accepted.

The following day she arrived at Swan Hunter (Dry Docks) Ltd, Wallsend for modifications, which were completed by November.