Williamson (born 1970 in Grantham, Lincolnshire) grew up in Grantham. Citing influences including mod subculture, Guns N' Roses, rave, black metal and Wu-Tang Clan, he previously fronted the electronic band Unity Crescent whilst also regularly performing as a solo singer-songwriter. He had also worked as a session musician with local artists as well as Spiritualized and Bent.
Williamson first met Fearn in 2009 after hearing him DJ at a small Nottingham club called the Chameleon, where he was playing his own rough edged and minimal grime inspired tracks. Sleaford Mods began when Williamson's friend suggested that he combine his vocals with a music sample from a Roni Size album. Originally the project was called "That's Shit, Try Harder", later changed in reference to Sleaford, a town in Lincolnshire not far from Grantham.
Williamson formed the band with Simon Parfrement, who he worked with alongside a studio engineer at Rubber Biscuit Studio in Nottingham on their first four albums. Parfrement left the music production to Andrew Fearn after the release of the 2012 album Wank, the first album to feature Andrew Fearn, but continues to play an important role in the band as their photographer and media producer.Fearn (born 1971 in Burton upon Trent) grew up on a farm in Saxilby, Lincolnshire. He was recruited by Willamson after he heard him play at The Chameleon Arts Cafe in Nottingham.