Walker began his single seater racing career in 2002 in the UK Formula Ford championship, finishing the year in 17th place.

As a result of his achievements during the season he was nominated for the National Racing Driver of the Year at the annual Autosport Awards.

He also took part in two F3 Euroseries rounds, at Hockenheim and Brands Hatch, but failed to score a point in the four races he entered.

He finished his maiden year 19th in the final standings, with the highlight being a win in front of his home crowd at Donington Park.

He and Rob Bell got two class wins out of five races driving a Ferrari 458 Italia, resulting runners-up in the GTE-Pro drivers and teams championships.

In 2012 he won the Paul Ricard race for JMW together with Jonny Cocker, and retired at the 24 Hours of Le Mans.