In 1970, Flint formed McGuinness Flint with Tom McGuinness, former guitarist and bassist with Manfred Mann. They reached number 2 in the UK Singles chart with "When I'm Dead And Gone", which was followed in 1971 by another hit single, "Malt and Barley Blues", which peaked at number 5. They also cut their self-titled debut album in 1970, which reached the Top 10 of the UK Albums Chart in 1971. However the early success of the group proved to be short lived. Despite featuring the production skills of Glyn Johns and the accompaniment of pianist Nicky Hopkins, their second album Happy Birthday, Ruthy Baby proved to be the end of the original line-up. Multi-instrumentalist band members Benny Gallagher and Graham Lyle left the group following its release. McGuinness and Flint teamed up with Dennis Coulson and Dixie Dean to release the album Lo and Behold in 1972, which consisted solely of obscure Bob Dylancovers. Shortly after this Coulson left. Despite the release of two further albums and a Greatest Hits collection in 1973, the band split in 1975. Flint played with the Bonzo Dog Band from 1971 and appeared until their final album, Let's Make Up And Be Friendly.
Flint's last band based venture was in The Blues Band, a supergroup composed of Dave Kelly, Gary Fletcher, McGuinness and fellow Manfred Mann veteran singer Paul Jones. Their debut, The Official Bootleg Album, was released in 1980, and Flint also appeared on their follow-up albums Ready (1980) and Itchy Feet (1981) before departing.
In 1995 Flint appeared on the BBC television documentary, Rock Family Trees, to discuss the history of the Bluesbreakers and the many off-shoots of the band. By that time he was working as a porter at Mansfield College, Oxford, from where he retired in 2007.