The Bristol Type 142M Blenheim was as a light bomber, designed by Frank Barnwell and built by the Bristol Aeroplane Company. It evolved from the Type 142 aircraft, which had been built in 1935 for private ownership by the Daily Mail proprietor Lord Rothermere. Rothermere was so impressed with the aircraft that he named it 'Britain First' and presented it to the nation for evaluation as a bomber. The duly modified design became the Bristol Type 142M Blenheim Mk I.

At the outset of war in 1939, advances in aeronautical technology had rendered the Blenheim obsolete. It no longer had the advantage of speed over its adversaries and its climbing ability was poor; it was under-armoured, under-armed and suffered from limited visibility from the cockpit at night. As a consequence, it suffered severe losses and was withdrawn from Bomber Command in 1942.