A Dambuster's medal is expected to fetch thousands at auction next week to raise money to build a life-saving dam in Africa.
The award, given to a 21-year-old pilot who later flew one of the 19 Lancaster bombers on the daring Second World War mission, could raise up to £40,000 for the project in Uganda that hopes to supply nearly 100,000 people with safe, clean water.
Flight Lieutenant John Vere "Hoppy" Hopgood received the Distinguished Flying Cross and Bar less than a year before he took off on the famed but fateful mission to destroy three dams deep in Nazi Germany.
The young airman never returned, although the story of valour and heroism behind the medal should help raise a huge sum for WaterAid when it is auctioned next week.
David Kirk, of auctioneers Morton & Eden said the lot, which includes a letter from Hopgood's commander informing his mother of his death, was "undoubtedly" one of the most iconic Distinguished Flying Cross medals to be auctioned in years.
He said: "Flight Lieutenant Hopgood's family has agonized over the decision to part with the medal but feel that John Hopgood himself would approve.
"He was evidently a very thoughtful and idealistic young man who, we believe, would be glad to know that the proceeds from the sale of his medal will go towards the building of a much-needed sand dam to benefit thousands of people in Uganda.
"The new dam will form a fitting memorial to Hopgood's heroism and self-sacrifice on the Dambusters' mission, of which his family can be duly proud".
Thomas Benn, of WaterAid, said: "WaterAid is delighted that the family of Flt Lt John Hopgood will pay tribute to him through supporting our lifesaving work. "
Born in the village of Hurst, Berkshire, the pilot was educated at the prestigious Marlborough College, known today as the secondary school of the Duchess of Cambridge and Samantha Cameron.
As war broke out he was due to go to Corpus Christi College Cambridge to read law, but instead joined the Royal Air Force.
Despite his age he became a respected airman for his "considerable courage and cool nerve" while flying perilous sorties behind enemy lines.
He received the Distinguished Flying Cross in October 1942 and a few months later, in January 1943, he received his second award Bar.
Hopgood was selected to fly with 617 Squadron, who on the night of May 16-17 1943, executed Operation Chastise.
As part of Formation No 1 he followed Wing Commander Guy Gibson in a swoop on the Mohne Dam in West Germany.
Despite receiving serious wounds on the approach, the young airman flew low enough over the dam for the "bouncing bomb" to strike and destroy a hydroelectric power station.
Then, in a final act of selfless valour, he manoeuvred his Lancaster to gain enough height for his crewmen to bail out.
Those who survived were decorated and Gibson received the Victoria Cross.
The medal is being sold by his family in an auction on Tuesday December 15 at Morton & Eden Ltd, Nash House, St George Street, London.