Britain has already seen the first skirmishes in what could be a protracted battle between the Cameron government and organised labour. In the short term, schools and fuel suuplies could be hit by strikes; looking further ahead, there's talk of union protests targeting the London Olympics. Stephen Sackur speaks to Len McCluskey, leader of Unite, Britain's biggest union. He talks of defending workers' rights within the law, and outside it, if necessary. How far is he prepared to go?