ENGLAND centre Billy Twelvetrees is primed for his gainline war with Jamie Roberts after declaring he is expecting the most physical battle he has faced.

Roberts will spearhead Wales’ threequarter assault in Sunday’s RBS 6 Nations title clash at Twickenham as the main battering ram of the ‘Warrenball’ brand of power rugby favoured by head coach Warren Gatland.

Twelvetrees has faced several of the game’s most feared centres in Ma’a Nonu, Wesley Fofana and Brian O’Driscoll in a developing Test career spanning 11 caps.

But the 25-year-old Gloucester centre views fellow British and Irish Lion Roberts as offering the most muscular confrontation of all.

‘‘Yes, in terms of physicality Jamie Roberts will be the biggest challenge I have faced,’’ Twelvetrees said.

‘‘He’s a top-class player and he’s shown that in the years he has played for Wales and for the Lions. He’s always making breaks and getting over the gain line.

‘‘He’s one of these players you look up to and he’s such a good professional as well.’’ The collision between Twelvetrees and Roberts could be seismic – the former is 6ft 3ins and 16 stones, the latter 6ft 4ins and 17 stones.

Wales will launch their 2009 and 2013 Test Lions down the 12 channel at the first available opportunity and Twelvetrees knows the importance of issuing an early statement of intent in defence.

‘‘It’s huge for us as a team to get on the front foot straight away,’’ he said.

‘‘Rugby is a huge mental battle and psychologically you want to get on the front foot straight away and get the game going.

‘‘It’s the same with Wales, they’re going to know what’s coming and so will we.

‘‘But you’ve still got to deal with it. It’s about turning up on the day and performing.’’ Twelvetrees’ defence was an area of concern after he was flattened by Matt Toomua in last autumn’s victory over Australia as the Wallabies centre forced his way over the whitewash.

Since that 20-13 win at Twickenham, however, his defence has been watertight.

‘‘I’m working on it all the time, as the whole team do. It’s a huge part of our game. We want to put pressure on attacks and make them make errors,’’ Twelvetrees said.

‘‘You have to make your tackles and physically dominate the opposition. There’s a huge focus for me to get better at that.’’ England will enter the final weekend of the Six Nations with a shot at the title if they dispose of Wales.

Twelvetrees insists they have the expectation they will prevail over the champions on home soil.

‘‘Twickenham is the home of English rugby and it means so much to all the boys,’’ Twelvetrees said.

‘‘You don’t want to let anyone down and you want to do as well as you can. To play at home at Twickenham is what you get really excited about.

‘‘We took huge belief from coming from behind and winning the game against Ireland.

Doing it at Twickenham makes it extra special.

‘‘The Twickenham factor always gives you an extra per cent. I can’t put a number on it, but it gives you that extra belief and extra bit of energy when you are blowing.’’