Nuclear submarine HMS Triumph is to undergo a refit which should allow her to continue front-line operations for up to 20 years.

The Devonport-based boat has completed what amounts to its first commission – a 13-year period during which she spent 1,700 days at sea and travelled 370,000 nautical miles.

Triumph’s withdrawal from the front line was marked by a decommissioning ceremony shortly after the boat returned from visiting Brest in France.

The ceremony included VIP guest Lady Hamilton, the ship’s sponsor and wife of former Minister for the Armed Forces Archie Hamilton, who commissioned the submarine in 1991.

Also in attendance were former commanding officers, families of the ship’s company and civic guests from Teignmouth, Triumph’s affiliated town.

HMS Triumph has seen active service in many regions of the world, including the Afghanistan conflict.

Last year she deployed for seven months east of Suez, during which she visited Crete, Bahrain, the Seychelles, Diego Garcia and Singapore, returning to the UK at Christmas after an 8,000-mile odyssey.

The lay-up and refit period will include refuelling the submarine’s reactor and updating the sensor fit to introduce the new integrated Sonar 2076 suite – effectively bringing the equipment on board Triumph, as with her three sisters Torbay, Trenchant and Talent, up to the initial build standard of the successor Astute-class submarines.

Some of Triumph’s crew will remain with the submarine into the refit period, while some will be drafted to other boats.

After preparatory work, the refit itself starts next year, and will last for more than two years.

HMS Triumph was the last of the seven Trafalgar-class submarines to be built, and she was launched at the Vickers yard in Barrow-in-Furness on February 16, 1991.

One of the first of the T-boats to be fitted with Tomahawk Land Attack Missiles – TLAM cruise missiles – Triumph has a range of roles to fulfil for the Royal Navy, including the traditional hunter-killer role against enemy submarines, anti-shipping operations, and covert surveillance missions.