the mark 1 version of the iconic plane was one of the first spitfires to go into action , and was built in march 1940 .
but spitfire p9374 never made it to battle of britain as it crash-landed on french beach and lay hidden for 40 years .
at one point it was almost certainly flown by squadron leader roger bushell , later big x of the great escape fame .
the wreckage was discovered in 1980 and restored to its original condition . it is to be auctioned for £ 2.5 million .