In May 2013, while on holiday, he had a fall, breaking his pelvis. During treatment for the fall, Walker was diagnosed with the early stages of lymphatic system cancer. His condition was mild and treatable. In June 2013, it was reported that Walker was to receive chemotherapy in the coming months, and had cancelled plans to attend the 2013 British Grand Prix at Silverstone. Walker did not need chemotherapy anymore by July 2013. He was the guest star on BBC Radio 4's "Desert Island Discs" on 16 March 2014, where he selected Chris McNab's "How to Survive Anything, Anywhere: A Handbook of Survival Skills for Every Scenario and Environment" as his choice of book, and a hammock and pillow as his luxury items.