Born in North London, Allsopp grew up listening to dance music including breakdance, electro hip hop and house. An amateur breakdancer at eight, he started DJing at the age of 15 and he soon became submerged in DJ culture and UK garage.
After completing a degree in Furniture Design at Kingston University, he enrolled on a community music production course, so that he can better his awareness of sampling and its potential for use. He went on to practice on perfecting his sound by night and to take on a series of jobs by day.
Allsopp's debut album, titled The Outer Marker and released in 2002 by the independent label RGR Records, was a collection of songs about modern life, relationships, and the pressures of social situations. The album spawned three singles "Paradise (Lost & Found)", "Snowflakes" and "Triple Tone Eyes".
He did not gain fame until 2007, following his TV debut on BBC2's Later with Jools Holland, and then on the Channel 4 show The Friday Night Project, where he performed the single "Starz In Their Eyes", which reached No.2 in the UK Singles Chart; the following three singles didn't make the top thirty. "Starz In Their Eyes" was also featured in the Dolce & Gabbana Summer 2008 fashion show. Kylie Minogue also did a collaboration with him, "I Talk Too Much", for the American release of his Overtones album.
His third album, titled All Night Cinema, released in 2009, was preceded by first single "Embers", which had its premiere on BBC Radio 1 on 12 January 2009 and second single "The Day I Died", which became Jack's second highest charting single on the UK Singles Chart. Both singles peaked inside the top 20. The original choice for second single was "Doctor Doctor" but the single release was subsequently postponed.