In 1968 he formed the group Good Earth, which also included Colin Earl on keyboards, Dave Hutchins on bass, and Ray Bowerman on drums. They recorded the album It's Hard Rock And All That on the Saga record label, before Hutchins and Bowerman left. Joe Rush joined on washboard and the group adopted a more acoustic-based skiffle style. In 1970, with further line-up changes, the group became Mungo Jerry with hits to follow such as "In the Summertime". The song took Dorset only ten minutes to compose on a second-hand Fender Stratocaster while he was taking time off work from his regular job, working in a lab for Timex.
Father of six, Dorset lives with third wife, Britta, in Bournemouth. Interviewed in 2014, Dorset said, "Each of my three marriages has produced two children and I also have three grandchildren. I married my present wife, Britta, in 1995. We sold our home in her native Germany and moved completely to Bournemouth, where we’ve been based since 1994 and own two houses and a restaurant. I should be retired, but my brain is like that of an 18 year old."