Born to a working-class family, his father a machinist toolmaker,[2][3] Watt was hired as a pianist by Carl Barriteau at age 17, and served in the Royal Air Force during the Second World War.
Among his sidemen were Tubby Hayes, Ronnie Ross, Jackie Armstrong, Tommy McQuater, Bert Courtley, and Phil Seamen.
Watt became one of the better-known British bandleaders of the 1950s, winning an Ivor Novello Award for the song "Overdrive" and releasing their first LP record in 1958.
After disbanding his ensemble, Watt worked with Rix on stage shows and films, including the 1961 movies The Night We Got the Bird and Nothing Barred.
In 1964 he assembled the Centre 42 Big Band, and through the end of the decade wrote for television and directed singers Tommy Cooper and Freddie Starr.