Illegal migrants, believed to number over 600,000, more than the population of Manchester, are at the sharp end of the debate about immigration in Britain - yet are frequently hidden from public view.

In this powerful film, Fergal Keane, who has reported for BBC News from all over the world, finds out what life is really like for a group of illegal immigrants struggling to survive on British streets. He asks what drew them here, follows their battles to beat the system and shows how ineffective the authorities can be in dealing with them.