HMS Affray (P421)

HMS Affray (P421) was an Amphion-class submarine of the Royal Navy. Launched in 1945, she was lost in the English Channel on 16 April 1951, resulting in the death of all 75 crew members. Affray was the last Royal Navy submarine to be lost at sea.

The Affray was built by Cammell Laird in Birkenhead and commissioned in 1946. Amphion-class submarines were designed for service in the Pacific theatre during World War II, although Affray was completed after the war had ended. She undertook routine training exercises in the years following her commissioning.

On 16 April 1951, Affray departed Gosport, Hampshire for a simulated war patrol in the English Channel. She was due to surface off Start Point, Devon the following morning. When she failed to appear, a search operation was launched, involving numerous Royal Navy ships and aircraft.

The wreck of Affray was located on 14 June 1951, lying in Hurd Deep, approximately 260 feet (79 meters) deep. A subsequent investigation, conducted by a Board of Inquiry, concluded that the most probable cause of the sinking was a failure of the 'Snort' mast, a device used to allow the submarine to run its diesel engines while submerged at periscope depth. The failure likely caused rapid flooding of the submarine. Due to the depth and the complexity of recovering the vessel, Affray was left on the seabed and designated a war grave.