The fastest front wheel drive car in the 2016 & 2017 World Time Attack Challenge (WTAC) pro class, the WTAC Astra presented some unique opportunities for aerodynamic development. Working closely with Envirage who developed a rear suspension system maximising the available space for a diffuser, a very aggressive yet simple design was developed. With only a limited number of CFD runs conducted, a very competitive aerodynamic package was developed of which the full capabilities have yet to be realised.