As the threat of strike action by fuel tanker drivers looms over the Easter break, Mukul Devichand profiles Len McCluskey, the left winger who became general secretary of Unite in 2010. As the UK's biggest union and the Labour party's biggest donor, Unite is often in the headlines - many generated by its leader. Len McCluskey courted controversy by raising the prospect of strikes during the Olympics and was roundly criticised by both the Coalition and the Labour party. He has been an outspoken critic of Ed Miliband's leadership despite having played a key role in getting him elected. This week's Profile asks what Len McCluskey stands for and charts his journey from white-collar worker on the Liverpool docks to the most powerful trade union leader in the country.

Presenter: Mukul Devichand