London - England rewarded versatile forward Calum Clark for his impressive return to action after an eight-month ban for foul play by calling him up on Wednesday for the Six Nations.
Winger David Strettle and flanker James Haskell were recalled to the revised 33-man squad, while forwards Joe Launchbury, Tom Youngs and Mako Vunipola and flyhalf Freddie Burns have all been promoted to the senior group from the second-string Saxons after playing well in the autumn tests.
England's first game in the Six Nations is against Scotland on February 2 as they look to build on their second-place finish in the 2012 competition and their stunning 38-21 win over New Zealand on December 1.
"This is a very important year for England, with the Six Nations and the Saxons games to look forward to so there are some great opportunities for the players to demonstrate their club form at international level," Lancaster said. "The summer tour to Argentina will also be a great chance for those players pushing for a place, especially with some of our senior squad hopefully going with the Lions (on tour to Australia)."
The 23-year-old Clark, who plays as a flanker, No 8 or in the second row for Northampton, trained with England during last year's Six Nations but his international aspirations were put on hold after being found guilty of hyperextending the elbow of Leicester's Rob Hawkins.
The ugly incident tarred his reputation - despite his remorse - and cost him a chance of touring South Africa last summer but he has been given a shot at redemption by Lancaster, who knows Clark well from their time together at Leeds.
Clark will likely be the understudy to captain and flanker Chris Robshaw but his versatility makes him a good option for the bench.
Of the eight changes in all, Twelvetrees is arguably the most interesting as his form for Gloucester has been mixed. However, he has undoubted potential and offers a different kind of option to the hard-running style of fellow centres Brad Barritt and Manu Tuilagi.
England's 33-man squad for the Six Nations, announced by head coach Stuart Lancaster on Wednesday:
Forwards: Calum Clark (Northampton), Alex Corbisiero (London Irish), Dan Cole (Leicester), Tom Croft (Leicester), Dylan Hartley (Northampton), James Haskell (Wasps), Tom Johnson (Exeter), Joe Launchbury (Wasps), Courtney Lawes (Northampton), Joe Marler (Harlequins), Ben Morgan (Gloucester), Geoff Parling (Leicester), Chris Robshaw (Harlequins), Mako Vunipola (Saracens), Thomas Waldrom (Leicester), David Wilson (Bath), Tom Wood (Northampton), Tom Youngs (Leicester)
Backs: Chris Ashton (Saracens), Brad Barritt (Saracens), Mike Brown (Harlequins), Freddie Burns (Gloucester), Danny Care (Harlequins), Lee Dickson (Northampton), Owen Farrell (Saracens), Toby Flood (Leicester), Ben Foden (Northampton), Alex Goode (Saracens), Jonathan Joseph (London Irish), David Strettle (Saracens), Manusamoa Tuilagi (Leicester), Billy Twelvetrees (Gloucester), Ben Youngs (Leicester)