In 1993, Crooks became Ligier's chief designer under Frank Dernie, but with the arrest of team boss Cyril de Rouvre, which sent the team into decline, Crooks joined Simtek. While with Simtek, he designed both the S941 and S951. He stayed with them until the team left Formula One in the middle of 1995. He went back to Ligier, before joining Jordan. He later went to BAR and Minardi.
Crooks now works for Wirth Research, who designed the Acura ARX-01a, ARX-01b and ARX-02a.