When was V1 speed first introduced? Was it the result of a particular accident or series of accidents?
There were a series of RWY overruns during the days of the first group of jet airliners (early to mid 50's), possibly 3 within a 12 month period. Mainly early rotation resulting in the airplane stalling during the takeoff roll at full thrust. Such accidents caused review of the take off maneuver and birth of the RTOW (Regulatory Take Off Weight) calculations.
A description of 2 cases, 26th Oct 1952 and 3rd Mar 1953