Last December, the bookies were worried. For a moment it looked like a grime track might cause a Corbyn-sized upset and nick the Christmas No 1. Stormzy’s Shut Up had raced 99 chart places to No 8 in a week, carried on a wave of social media love. It featured the MC rapping over a synthetic ballad with snares as crisp as the melody was misty-eyed.

The track sounded like break-up music from the far future, but in reality the instrumental had been written by underground grime greats Ruff Sqwad well over a decade before. Never signed to a record deal, and with much of their work only available as dodgy pirate radio rips, Ruff Sqwad have remained obscure to all but the grime hardcore for years. But thanks in part to Stormzy’s endorsement these innovators are stepping back into the light.

A loose collective of DJs and MCs drawn from the estates of Bow in east London, Ruff Sqwad were DIY grime stars back when a career could be sustained by record sales alone. They self-released over 20 singles between 2003 and 2006, and kept 100% of the profits. While they never had witless A&R men on their backs, they also never had the blanket advertising and radio pluggers that major labels bring. As a result, their music was huge on pirate radio but non-existent in the mainstream. This punkish mix of integrity and obscurity has made their catalogue the stuff of legend: Ruff Sqwad records change hands for triple figures online.

“Our sound was very futuristic,” reminisces Ruff Sqwad MC Slix, trying to pinpoint why it’s taken until now for the crew to get their dues. “A lot of people appreciated it, but a lot of people just didn’t understand it…”

A compilation of the group’s instrumentals was reissued in 2012, finally making their thrilling futurism available to a new generation. Now, with Ruff Sqwad’s sound seeping into the mainstream, fans are getting a rare chance to see the originals in action. The group are reuniting for a one off show in Brixton this week. It will see core members Slix, Rapid and Dirty Danger reunited with Tinchy Strider, the MC who left the crew to achieve chart-topping success, securing a place in the history books for grime’s weirdest collab: a duet with the Chuckle Brothers.

The others don’t begrudge Tinchy his success: they’re happy with their status as underground greats. As Slix puts it: “Ruff Sqwad were the Arsenal of grime. We were always top four, but in terms of silverware, in terms of a big record deal, we never really got there. But like Arsenal are more about the football, we were more about the art.”

Ruff Sqwad will appear at Just Jam, Electric Brixton, SW2, Friday 29 April