A day-long test of speed and reliability for standard-equipment production sports cars, the Grand Prix d’Endurance organised by the Automobile Club de l’Ouest was not the first 24-hour car race – Columbus in Ohio hosted one as early as 1905 – but swiftly it became the benchmark, due mainly to ‘Bentley Boys’ who raced even harder than they partied.

The British invasion of what was to become France’s most famous race had a rapid start: China-born Canadian John Duff was the first to enter (much against W.O. Bentley’s better judgment) the inaugural edition of 1923 and, co-driven by Bentley’s only pro, Frank Clement, won in 1924. Local resistance, however, was strong in speed and number. Initially. Chenard et Walcker scored a 1-2 in 1923 and Lorraine-Dietrich registered consecutive wins from 1925. The former claimed the Triennial and Biennial cups of 1925 and the latter finished 1-2-3 on distance in 1926. Yet both then faded into racing obscurity.

These were trying financial times for myriad small-volume manufacturers, with mergers and takeovers abounding as bankruptcies beckoned. Bentley likely would have folded, too, but for diamond heir Woolf Barnato’s regular injections of cash. British names Alvis, Aston Martin and Lagonda joined Bentley and American makes Chrysler and Stutz, plus Itala of Italy – to outnumber the French by 1928.