This car was designed by Len Terry starting from a rather conventional concept, to house the three-liter V12 engine designed by Geoff Johnson initially for the sports category, but which already showed its merits on the 1967 McLaren M5A. Two units of the P126 were initially destined for the Tasman Cup and then converted to Formula 1, together with a third car. However, the P126 was soon replaced by the P138. With the P126, BRM finished fifth in the 1968 F.1 constructors' championship. Richard Attwood, Piers Courage, Pedro Rodriguez and Mike Spence drove the BRM P126.