The evacuation of British troops from France in 1940 did not end with Dunkirk. British forces were still being rescued two weeks later when Britain's worst maritime disaster of World War II took place.

On 17 June, 1940 the British troopship Lancastria was sunk off the Brittany port of Saint-Nazaire. More than 3,000 people lost their lives. A unique record of the disaster was captured by amateur photographer Frank Clements.

Click here to view images of the Lancastria disaster - some of which are published here for the first time.

The Lancastria, a converted Cunard liner, was carrying an estimated 6,000 servicemen and a number of civilian women and children when it was bombed by German planes.

The disaster is watched from HMS Highlander

The ship sank within minutes. At the time news of the disaster was suppressed by the British Government because of the impact it might have on the country's morale.

It was not until nearly six weeks later, on July 26, 1940, that the world discovered what had happened. The New York Times broke the story, printing some of the dramatic pictures of the disaster.

Helping survivors

In 1940 Frank Clements was a 30-year-old volunteer onboard the HMS Highlander, a destroyer that was being used to ferry troops from Saint-Nazaire harbour to the anchored Lancastria.

Navy personnel were not allowed to take cameras on board but as a volunteer in the naval stores, he managed to keep his camera with him wherever he went.

Photographs were his be all and end all

Frank Clements' brother Arthur

His younger brother Arthur Clements, now 84, says: "He was a photographic nut. He took thousands of 'prints' as he called them of his war experiences all over the world."

But as well as taking pictures he also played his part in the rescue operation, downing his camera to help survivors.

"He did all he could," recalls his brother. "He even pulled a little baby out of the sea."

Survivors were covered in oil from the ship's fuel tanks

"He talked afterwards about the soldiers who had been ordered not to abandon their rifles. He watched them drowning under the weight of their heavy weapons and said he shouted at them to let go of them. Sadly many didn't listen."

Valerie Billings of the Portsmouth Naval Museum, who interviewed Mr Clements before his death in 1999, says it was an enormous stroke of luck that he was able to take the photographs.

"It was an amazing coincidence, firstly that he had a camera on board at all. Secondly, he had no film for the camera but happened to meet a sailor on his way to Saint-Nazaire who swapped him a camera film for a pair of socks from the NAAFI stores and it was with that film that he took these pictures."

'Invaluable' record

When he returned to the UK, Mr Clements handed over prints of his photographs to a man he met in a pub. The pictures were then sold to the press, although Mr Clements never made any money from them.

The photographs are priceless

Robert Miller of the Lancastria Association

The pictures have now become invaluable to the Lancastria Association in their campaign to make the story of the doomed ship more widely known.

The Association's Robert Miller, who will be heading out on a pilgrimage to Saint-Nazaire on the 60th anniversary of the disaster in June, says: "The photographs are extremely important, priceless in fact, to us and to the whole fabric of the story."

"If it wasn't for the fact that Frank Clements was on board the Highlander and that he was a keen photographer, there would be no pictures of the disaster whatsoever."