Walker had announced in early October that he was retiring from radio after 58 years having been previously diagnosed with idiopathic pulmonary fibrosis (IPF).
He was born in Birmingham and left school at the age of 15 to train to become a mechanic, later taking a job as a car salesman.
He found an outlet for his passion for music with a Friday night slot as a disco DJ under the name Peter Dee.
Walker began his radio career in 1966 on Swinging Radio England, an offshore pirate station.
He later moved to Radio Caroline, where he became a household name hosting the hugely popular night-time show.
Walker went on to join BBC Radio 1 in 1969, continuing until 1976, with him later moving to San Francisco, where he recorded a weekly show broadcast on Radio Luxembourg.
He returned to the UK in the 80s and presented Radio 1’s Saturday Stereo Sequence.
After working on various BBC stations, he left Radio 1 for good in 1995 and three years later he was offered his own weekly show on Radio 2, before taking over Drivetime.
He earned a reputation as a DJ who accorded more importance to the records he played than the chat between tracks, with names he pioneered including Lou Reed, Fleetwood Mac and The Eagles.
In October 2003, Walker underwent chemotherapy and an emergency operation for non-Hodgkin’s lymphoma.
He told his listeners live on air of the diagnosis and later revealed that he “died” on the operating table three times during surgery to repair his burst intestine.
The condition IPF is one “in which the lungs become scarred and breathing becomes increasingly difficult”, according to the NHS.
The NHS website says it is not clear what causes the condition and that treatments can reduce the rate at which it worsens, but that there is “currently no treatment that can stop or reverse the scarring of the lungs”.