HMS/M Sovereign was the second of six Swiftsure class nuclear propelled submarines, all of which were built in the Barrow shipyard. Classified as Fleet Submarines, or more commonly known as Hunter Killers. Their role to protect the Royal Navy's squadron of nuclear armed (Polaris) submarines, to undertake surveillance and monitoring of manoeuvres of hostile nations, but specifically tracking the submarines and shipping of the Soviet Union during the Cold War, and to participate in both anti-submarine warfare and attacks on ships and terrain should the need arise.

On the 20th of October 1976, HMS/M Sovereign surfaced at the geographical North Pole, as part of operation Brisk.