The sextet will be playing with its original line-up at the London venue on October 6, but will play The White Hart in Corby the night before.
Since their successful comeback which started in 2014, the band have tour nationally and internationally, racking up appearances at every major metal festival in the UK and released the album Lost Ritual in 2016.
Raging Speedhorn view this reunion as a celebration of their 20 year career.
Guitarist Gaz Smith, who left the band in 2008, will be returning with original guitarist Tony Loughlin and bassist Darren Smith.
Gaz said: “Starting Raging Speedhorn with the guys 20 years ago changed my life completely.
“It was and still is a huge part of me. I’ve never really been one for going back, as far as playing music goes, but to celebrate the twentieth anniversary with a special, absolutely one-off show was just too fun a thing to turn down. It’s going to be amazing. I can’t wait."
Support at The White Hart is by Scourge and Sharkteeth Grinder.
Doors 7pm, ticket cost £8 on the door.
In London, support is by NOLA legends Crowbar, Charger and Scurge.
The band is working on their follow up to Lost Ritual.
Advance tickets for the London show cost £22 before fees and are available via https://myticket.co.uk/gigs/raging-speedhorn-london-2018-10-06-18-00