Born into a musical family in Cambridge, Renwick learned to play the clarinet and dabbled with saxophone, flute, cello and the recorder family before discovering the electric guitar at the age of 14.

During his teens, he formed several short-lived amateur bands before joining the Wages of Sin, a locally-successful semi-pro group. The band later became Little Women and started getting gigs at London clubs, where Renwick was spotted by DJ John Anthony who recommended him for Jackie Lomax's backing group.

In 1969, Renwick joined Junior's Eyes for non-stop touring all over the UK and Europe. During this period, the band also did some recording with producer Tony Visconti, who introduced them to David Bowie - as a result of which they played on Bowie's Space Oddity album and also did some gigs with him. After just one album, the band broke up in 1970 caused by the ill-health of leader Mick Wayne.

While living in Ladbroke Grove, Renwick met Canadian Cal Batchelor and formed the Poco-influenced Quiver, releasing two albums, Quiver and Gone in the Morning, and playing many gigs. Meanwhile session work continued.

In 1972, with Batchelor gone and Peter Woods joining on keyboards, Quiver teamed up with Iain and Gavin Sutherland as the Sutherland Brothers and Quiver. The collaboration had some success, touring the US supporting Elton John and releasing several albums.

But by 1976, Renwick was ready to leave and work as a freelance session guitarist.

Between 1976 and 1980, Renwick recorded and toured with Al Stewart and with Andy Gibb in the US. Session work included Cliff Richard, Gary Brooker and Elton John. He also formed a group of studio musicians called Lazy Racer, recording two albums.

Studio work continued during the 1980s and early 1990s, notably including Pink Floyd's Division Bell and gigs such as Live Aid.

Between 1994 and 1995, Renwick performed 110 show with Pink Floyd, including the live recording of Pulse.

In the late 1990s, Renwick toured with Mike and the Mechanic and Paul Carrack.

He then moved to Cornwall and now plays with a local band called the Bucket Boys, but occasionally also takes part in gigs such as the Live 8 concert with the reunited Pink Floyd in 2005.