[3] The song was written by band leader Francis Rossi and roadie / harmonica player Bob Young on a table napkin in the dining room of a hotel in Perranporth, Cornwall, in 1971.
A demo was cut with Rossi playing guitar and bass, with Terry Williams on drums.
The group changed the arrangement from a slow blues song, doubling the tempo, and recorded it mostly live using their stage gear and amplifiers.
[4] On the single release, the song fades out, while the album version is about thirty seconds longer and has a conclusive ending.
[4] It was the second number played at their Live Aid gig in 1985[5] and it inspired Apollo 440's 1999 single "Stop the Rock".