A letter from a Dambusters hero who launched the iconic bouncing bomb that destroyed its target has been discovered hidden behind a signed print.

       Flying Officer Edward Cuthbert Johnson recalls in the note, right: “I am an original 617 Squadron member and in fact dropped the Barnes Wallis bomb which breached the ‘Eder’ dam.”

       He was replying in 1989 to a request for a copy of the menu from a celebratory London meal held a month after the May 16 1943 raid intended to cripple Nazi Germany’s industrial production.

       F/O Johnson – at 31, known as the “old man” of the 133 aircrew – was a bomb aimer. The Eder, Mohne and Sorpe reservoirs generated electricity and water for Ruhr factories arming Hitler’s Second World War campaign.

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       While he could not provide the photocopy, he replied to the enquirer: “If you have anything else you wanted signing – send it and I will sign and return.”

       His note was found by chance by Ewbank’s Auction House specialist Denise Kelly, attached to a Dambusters-themed print in the seller’s home. She said: “Just as I was leaving, I glanced up at a Dambuster-related signed print on his wall. There were several plastic wallets of newspaper clippings etc. pinned to the back.

       “Then I just saw the corner of this letter peeping out.”

       The letter is tipped to fetch ￡300 to ￡500 when sold by the Send, Surrey firm on May 30.

       F/O Johnson was awarded the Distinguished Flying Cross. After the war, he returned to his wife May in Blackpool and became director of Sellers Fireplaces.

       He died aged 90 in 2002.