He did occasional Formula 1 commentaries during the 1970s before going full-time for the 1978 season. Walker was asked by the head of BBC Sport Paul Fox to commentate on the Commonwealth Weightlifting Championships in Bristol, and he asked the weightlifter Oscar Slate to educate him on the sport. He covered motocross (initially for ITV and BBC) during the 1960s and rallycross in the 1970s and early 1980s. He occasionally commentated on scrambling (now motocross) motorcycle racing and rallying during the 1960s through to the 1980s. Walker covered the British Touring Car Championship (BTCC) for the BBC between 1969 and 1971 and also 1988 and 1997, and the Macau Grand Prix for Hong Kong TV on nine occasions. He joined the Channel 7 commentary team of the Bathurst 1000 Australian touring car race in 1997 and 1998. As the BBC began to broadcast additional forms of motor racing, he commented on Formula 3, Formula Ford and truck racing.