Seventy-five years ago on this date, George P.W.S. Bullman took the prototype Hawker Hurricane, K5083, designed by Sir Sidney Camm, into the air from the airfield at Brooklands, Surrey.
It was (despite the focus on the more famous sister aircraft) the decisive aircraft in the Battle of Britain, five short years after that first flight. Hurricane pilots accounted for more enemy aircraft shot down during the battle than all the other defences combined. As Francis K Mason put it in his book on the type, "The RAF ... had to have the Hurricane". One key reason why the Hurricane was critical was that Hawker's were able to carry forward their well tried biplane technology and factories using the systems into an effective - albeit limited development potential - eight-gun monoplane fighter. Even with all the short cuts Hawker's used, production of sufficient Hurricanes was, in the words on another battle 'a damn close run thing'.
These two photographs of the prototype show both how it differed from production Hurricanes, and also a number of changes K5083 underwent in its own early career.
Notable changes are the re-arrangement and extra bars on the canopy after excessive flexing; the removal of the tailplane struts; the extension of the radiator bath as well as many other small items - as expected in a prototype's development.
Differences to production aircraft are also numerous, but one that always intrigued me is the change in the shape of the undercarriage door.
[Images originally Hawker Aircraft / RAF Official, I believe.]