During the 1960s Walker's racing career faltered (he was the 1969 British Formula Ford Champion and finished third in the 1969 European Formula Ford Championship), however finally broke through racing a Lotus in Formula Three during 1971.
Durante a década de 1960 a carreira de Walker fraqueou (foi o Campión británico de Fórmula Ford de 1969 e terminou terceiro no Campionato de Europa de Fórmula Ford de 1969), pero finalmente destapouse correndo cun Lotus na Fórmula Tres durante o ano 1971.