In my Birkin blower 4 1/2-litre Bentley piece in the June issue it was not explained that the 50 Bentleys of this kind, which Birkin got W O to make against his better judgement, were required for homologation for the 1930 Le Mans race. The ruling was to ensure that only catalogue, indeed production, cars ran in the 24-hour sports car race.
At first the regulations required that duplicates of the entered cars should be bought to the circuit; later that the entrants had to swear on their honour that they had built and sold, or at least stocked, 30 similar cars.
The complexion of the race was changed in 1949, when prototype sports cars were accepted. However, standard cars continued to have their place, provided it was declared that at least ten of the kind raced had been sold. (The SO rule came in later, hence the Birkin request to W O in 1929.) Then the number required rose to 100, with 12 consecutive months allowed for these catalogue cars to be completed. In fact only five Blower Bentleys were sold before the race in June 1930, the remainder by September 1931, with one exception.
One has to assume that the smallest of French manufacturers complied, for they wouldn’t cheat, would they? However, French officials have sometimes managed to eliminate those they felt were a threat to French successes, as with the 1908 GP Austins, unacceptable with their Rudge detachable wheels, Colin Chapman’s 743cc Lotus 23, with which he hoped to win the 1962 Le Mans Index of performance, was rejected at the last moment as “not in the spirit, and unsafe”, when it looked likely to spoil a Panhard handicap win, and you will recall the disqualifications of the victorious Minis in the 1966 Monte Carlo Rally because of a supposed lighting infringement.
The battle for the Brooklands lap record between Don (Sunbeams) and Birkin (Bentley) got a bit obscure in my story; it went actually went: 1929, Don, 134,24mph; 1930, Birkin, 135.34mph; Don, 137.58 mph; 1932, Birkin, 137.96mph.