1973 saw Ertl continue to mix Formula Three and Touring Cars, with little success, until the September, when at the side of Derek Bell, they would win the RAC Tourist Trophy, with both drivers each winning their respective heat, to take an aggregate victory.
1973 viu a Ertl continuar mesturando a Fórmula 3 e Touring Cars, con pouco éxito, ata que en setembro, xunto a Derek Bell gañaron o RAC Tourist Trophy, con ambos pilotos gañando cada un a súa respectiva eliminatoria, para lograr unha vitoria global.