The cars of Frank Williams are as varied and elusive as Frank himself, his entries in Formula One starting in 1969 with a Brabham BT26 and then moving on to the De Tomaso factory team, with Piers Courage as his driver. This period was followed by two seasons with March cars, with Henri Pescarolo and Carlos Pace, and backing from the French Motul oil company, and in 1972 his own long-awaited car, designed by Len Bailey, but finished off by Ron Tauranac, appeared at Brands Hatch for the British Grand Prix driven by Pescarolo and at the end of the season driven by Chris Amon. It was called a Politoys, after its sponsor, and had the design number FX3/1. In 1973 Frank Williams got sponsorship from Iso Rivolta, Marlboro and Fina Petrol, to replace Politoys, who had pulled out of racing, so the FX3/1 was re-christened an Iso Rivolta Marlboro and a second car, FX3/2, was added to the team.
A new start was made for the 1973 season in Europe with two new cars designed by John Clarke. These were IR/01 and IR/02, which appeared at the Spanish GP driven by Nanni Galli and Howden Ganley. In 1974 a third IR series car was added to the team and for 1975 the cars have been re-christened once more, now being called Williams (though Motor Sport has called them this all along) and the serial numbers have been changed from IR (Iso Rivolta) to FW (Frank Williams). When IR/02 was destroyed in a crash at the Nurburgring in 1973 it was completely rebuilt around a new monocoque chassis frame, and should by rights have been IR/03, though in fact it retained the number IR/02. Consequently, when the third car in the IR series was built, it was actually the fourth car built, and should have been IR/04, but due to the previous mix-up it was IR/03.
In some ways we have already lost track of the cars of Frank Williams, but it is hoped that this will salvage something from the chaos.