The crew that perished in the crash were all in their early 20s

The bomber hit the slopes of Carn Llidi near St Davids in thick fog on 4 June 1943, killing all four on board.

One of the aircraft's propellers, found on the hillside, forms part of the memorial at nearby Whitesands Beach.

The daughters of pilot Robert Lawrence and navigator Hulbert Robertson travelled to Wales for the ceremony.

On Saturday - 62 years to the day of the crash - they were joined by civic and military representatives to unveil the memorial and plaque.

The doomed aircraft was part of a formation on a delivery flight to RAF St Eval in Cornwall, travelling via South America, the Ascension Islands and North Africa, when the formation separated due to poor weather and thick fog.

The story of the flight has been recently put together by author and historian Steve Jones, who said: "It was a very foggy day and the mountain was shrouded in fog and after flying from North Africa they thought they were over the sea.

We first visited the site last year and found small aluminium pieces of the aeroplane on the hillside which made it seem more real Airman's daughter Gwen Scoggins, right

"About five years ago a walker in the area found one of the propeller blades."

This discovery led Mr Jones to try to contact relatives of the crew.

Among those who crossed the Atlantic for Saturday's ceremony are Mr Robertson's daughter, Gwen Scoggins, and her half-sister, Shirley Wetzel.

Ms Scoggins said: "All we had ever heard about what had happened was that he had crashed into a mountain in Wales.

"It's meant a great deal to our mother because, for 60 years, she did not know what had happened.

"Steve has been wonderful and if it were not for him we would still not know."

The crew, also made up of co-pilot James Jackson and engineer William Brown, were all in their early 20s. Only Mr Lawrence and Mr Robertson were married with children.

The memorial is made from one of the bomber's propellers

Ms Scoggins, who travelled from Irving, near Dallas, Texas, said she was pleased that the memory of those who had lost their lives in the conflict was being kept alive.

"We first visited the site last year and found small aluminium pieces of the aeroplane on the hillside which made it seem more real," she said.

"All the people that we spoke to there said how they appreciated the Americans coming over.

"It will be emotional. I'm looking forward to meeting the daughters of the pilot."