The Royal Navy submarine sank near the Hurd Deep, seven miles north-west of Alderney, with the loss of all 75 crew.
The vessel set out on a training exercise on 16 April 1951, but did not report in the following day. It was found in June 1951, but was left where it lay. The Royal Navy’s official inquiry concluded that the sub sank because the snort mast snapped because of metal fatigue, but other theories have also been put forward.
It is the worst Royal Navy submarine accident since the Second World War.
The service will be held at the HMS Affray Memorial at Braye Harbour at 10.30am.
The families of lost crew members are unable to attend due to Covid-19 travel restrictions, but States members, ex-servicemen and the island’s vice-president, Graham McKinley, will be joined by the public to pay their respects with the laying of wreaths.
The Rev. Jan Fowler will lead a short service of remembrance at the memorial which looks out across Braye Bay towards the Hurd Deep, where 50 crew, 21 officers on training duty and four Royal Marines died.