France cannot roar away from their blocks, warns England’s Billy Vunipola

• England No 8 says visitors will be dangerous• ‘When they get momentum they are hard to stop’Billy Vunipola has urged England to fly out of the blocks at Twickenham on Sunday, warning his teammates they cannot afford to let France build up a head of steam.England are hot favourites for victory against France, who collapsed to a humiliating defeat by Wales last Friday and have not won a Six Nations match at Twickenham since 2005. Against Wales, France raced into a 16-0 half-time lead, only to capitulate after the break, prompting Jacques Brunel to make six changes and recall Mathieu Bastareaud…