Their names were all chosen from villages ending in -ham. The minesweeper was named after Portesham in Dorset, using an alternative spelling for the village.
Portisham served in the Royal Navy from 1956 until 1964, when she was transferred to the Royal Naval Auxiliary Service (RNXS).
On 15 April 1973, Portisham assisted a Royal Dutch Navy Breguet Atlantic aircraft no 257 which ditched off Wassenaar, Netherlands.
Portisham was removed from service in 1983. After her sale in 1989 she was laid up and for sale in a boatyard in Essex. She was procured for conversion to a liveaboard ship by an Irish national in 2007 and is currently the second biggest private vessel under the Irish flag.