The Blackout are set to open the main stage on Saturday at Reading Festival and Sunday at Leeds.
Joining a bill that already boasts The Subways, Bloc Party, The Raconteurs and Editors, the Welsh metallers will make their first appearances at the sold out festivals.
Elsewhere garage rock trio White Denim have cancelled their apperance and have been replaced by rising pop troubadour Esser on the Festival Republic Stage.
Reading and Leeds Festivals 2008 will take place at Little Johns Farm, Reading and Branham Park, Leeds from 22-24 August with The Killers, Rage Against The Machine and Metallica headlining.
The Enemy, Biffy Clyro, The Last Shadow Puppets, MGMT, The Cribs, Babyshambles, Dirty Pretty Things and many more are also set to appear. Click HERE for the full Reading line-up and HERE for the Leeds bill.
Comedy, film, cabaret acts and late night entertainment are yet to be announced for the Alternative Stage. Check back for updates on the festival.