Ronnie Peterson in his 1974 Lotus 76, with the bizarre but interesting (and, sadly, ineffective) biplane rear wing. Peterson was in the odd position of racing with the #1 on his car despite not being the champion (Lotus had won the constructor’s championship in ‘73, but his teammate Emerson Fittipaldi left at the end of that season for MacLaren). In keeping with the F1 numbering system, Lotus had #1 and #2 for their drivers in 1974, giving the remaining Peterson the numero uno.
Although this photo isn’t labeled as such, I believe it was taken at Jarama for the Spanish Grand Prix.
