Origination
The composer's son Austin Coates recounted in a radio interview for the BBC that the march was not actually written for the film and had in fact been completed a few days before he was contacted by the producers. The composer had apparently been carrying out an exercise in composing a march in Elgarian form, which is the same structure as the famous Pomp and Circumstance Marches.
Coates had a profound dislike of writing film music and turned down numerous requests; he was prevailed upon by the producers, who told him this was "a film of national importance." He was initially inclined to refuse the commission but, on hearing more about the film, came to the conclusion that the piece he had just completed might just be the very thing.
Read more about this topic: Dambusters March