Experiencing their greatest success in the early 1970s, with a changing line-up always fronted by Dorset, the group's biggest hit was "In the Summertime", which sold 30 million copies worldwide and is the biggest-selling single of all-time by a British band.

[5] Mungo Jerry came to prominence in 1970 after their performances at the Hollywood Music Festival at Newcastle-under-Lyme, Staffordshire, on 23–24 May, which was their first gig under this name,[6] inspired by the poem "Mungojerrie and Rumpleteazer" from T. S. Eliot's Old Possum's Book of Practical Cats.

The trio played more gigs and landed a regular slot at the Master Robert Motel in Osterley, Middlesex, where they soon built up a following, including banjo, guitar and blues harp player Paul King who eventually joined the band, making it a four-piece.

After Rush left, Mike Cole was recruited on double bass, and this line-up recorded the first seventeen Mungo Jerry tracks which made up the first album and maxi-single including "In the Summertime".

According to Joseph Murrell's The Book of Golden Discs (1978), "Mungomania" was possibly the most startling and unpredictable pop phenomenon to hit Britain since The Beatles.

His intention to broaden the group's appeal by recruiting a drummer led to King and Earl trying to sack him, but the management, regarding Dorset as inseparable in the public eye from Mungo Jerry, fired them both instead.

[1] In 1975, Earl returned to play keyboards, drummer Peter Sullivan joined and percussion player Joe Rush, part-time member of the band in earlier days, also came back for a while.

[citation needed] In 1980, another Dorset song, "Feels Like I'm in Love", originally written for Elvis Presley, and recorded by the band as a B side of a single, became a British number one hit for Kelly Marie.