A pair of letters by the inventor of the bouncing bomb, Sir Barnes Wallis, will be sold at International Autograph Auctions on March 5. 

Sir Wallis was the inventor of the bouncing bomb

Each is valued at £200-300 ($282-424). 

The letters were written to a friend in December 1944, shortly after his bomb was used in the first raid, and in May 1945. 

In the first letter he writes: "It was not until I had had time to relax that I realised how utterly tired out I was. 

"For the past year I have had to force myself to go on; & I must have been as near a crash as one would care to go."

A set of medals awarded to Dam Buster Flight Lieutenant Trevor-Roper realised a record £148,000 last year.  

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