SAILOR Steven Somerville died after plunging 40ft down a missile tube in a Trident submarine.

The 25-year-old Royal Navy mechanic from Tyneside fell while carrying out routine checks in the missile shaft on HMS Vengeance.

The Royal Navy has launched an official inquiry.

Mr Somerville, married with a baby, died following the fall on October 6 while the nuclear submarine was harboured at the Trident refit facility, at the King's Bay US Naval base, in South Georgia, USA.

The 16,000-acre base is a regular port of call for British Trident submarines seeking routine inspection and repairs.

Mr Somerville, who had been in the Navy for three years, and achieved the rank of Naval Rating, was usually stationed at Faslane, on the river Clyde in Glasgow.

He had travelled to the US with the 135- strong crew under the command of Steve Upright.

His parents Robert and Jean, his twin brother, Andrew, and his wife are being comforted by relatives.

They are too upset to speak about his death and are still awaiting arrangements for his body to be flown home to Tyneside so a funeral can take place.

The crew and commander of the Trident were among 500 people who attended a memorial service in the chapel at King's Bay.

Commander Terry Evans, the base's public affairs officer, said: "A mixture of British and American servicemen and women attended the memorial service in honour of Steven and to help others get over their grief."

A Ministry of Defence spokesman said: "There are not thought to be any suspicious circumstances, but an independent board of inquiry has been set up to investigate the accident.

"The commander and the ship's crew are all deeply shocked by his death and extend their sympathy to Mr Somerville's family."