Halsall's most commercially successful recording is his work on the album "The Rutles" (1978), which reached the top 20 in the UK, on which he plays many of the instruments and provides lead and backing vocals – most notably on the tracks "Doubleback Alley", "With a Girl Like You" and "Get Up and Go". Eric Idle was cast in his place in the accompanying film and Halsall only featured in a very minor cameo role as "Leppo", the fifth Rutle who became lost in Hamburg.