Keith Mansfield was born and brought up in Slough. He joined a local boy's band, initially playing the oboe, before moving on to the cornet and finally the alto sax, which he went on to play professionally. However, he was always more interested in writing, and gained fame as a composer and arranger.

He was responsible for composing many famous TV theme tunes, including Grandstand, Wimbledon, BBC Athletics, and The Big Match on ITV. Also, some of his stock music was often heard on programmes like The Sweeney and Are You Being Served?

Mansfield was also a successful musical arranger, working on two Number 1 records in the 1960s - 'Everlasting Love' by The Love Affair, and 'Ob-La-Di Ob-La-Da' by Marmalade. He also worked with artists such as Tom Jones, Dusty Springfield and Robert Plant.

Early in his career he worked with bandleader Joe Loss, and much of his later work was in the field of jazz.