HRH The Princess Royal arrived by helicopter to declare the new £3.1 million John Fieldhouse Building open. Courtesy Royal Navy Submarine Museum.

HRH The Princess Royal officially declared the new John Fieldhouse Building at the Royal Navy Submarine Museum in Gosport open on September 8 2005.

Named after the late Admiral of the Fleet, Lord John Fieldhouse of Gosport (1928-1992) – the most senior submariner in British naval history – the building is dedicated to all submariners who lost their lives in the Second World War.

The submarine-shaped, zinc-clad steel structure is part of a £3.1 million extension to the museum.

"This museum has already got a very high standing," HRH The Princess Royal told the gathered dignitaries. "The new building," she added, "will continue that reputation and respect."

Commander Jeff Tall, museum director, takes HRH the Princess Royal on a tour of X24, the only remaining example of a British X-craft which saw service during World War II. © 24 Hour Museum.

Lord John Fieldhouse enjoyed a highly decorated career in the Royal Navy, which saw him take overall charge of British forces during the Falklands War in 1982. He went on to become First Sea Lord and then Chief of Defence Staff before his premature death in 1992 at the age of 64.

Accompanied by her three children, Lord Fieldhouse’s widow was among the many guests at the opening.

Having previously been to the site to dig the first sod and hammer in the last nail in the roof, she was impressed with the final result but added that her late husband would have been embarrassed by its name.

"The first thing he would have said," she explained, "is ‘what the hell’s it doing named after me’"

The building is shaped like a submarine and is clad in zinc and steel. © 24 Hour Museum.

A new interactive Science and the Submarine gallery has been created on the first floor of the new building, which also houses X24. The only remaining example of a British X-craft that served in the Second World War, X24 has a cut-away section to allow visitors a view of the inside.

"The building’s primary heritage purpose is to provide for the long term care of X24," explained Sir Roy Newman, chairman of the museum’s trustees. "She’s a jewel in the nation’s maritime heritage crown and a reminder of the extraordinary sacrifices of earlier generations of submariners."

In addition to the museum’s interactive education collection, the building also has lecture space and room for corporate entertainment as well as a 60 metre square area for temporary exhibitions.

"This building’s a very important part of the history of ships but particularly of submarines," said HRH The Princess Royal, "and it helps us to try to understand why anybody would wish to serve in a submarine!"

Part of the museum's collection, HMS Alliance gives visitors an idea of what it's like to serve in a Cold War-era submarine. © 24 Hour Museum.

Joking aside, she added "for the rest of us it starts with admiration and it goes up from there."

Her words were echoed by Admiral Sir Alan West, the First Sea Lord: "Historically there’s no doubt submarines were very, very dangerous. In the First World War" he said, "one in four submariners died and in the Second World War one in three was killed, so it’s a marvellous commemoration to Lord John Fieldhouse, but also to all those men."

The building was supported financially by a number of organisations including the Heritage Lottery Fund, which awarded a grant of £2 million to the project.