File on 4 hears from Britons jailed for hiding people in their cars. They reveal why - and how - they did it.

They were paid to smuggle people across the Channel by gangs based in London and the North West.

This unofficial migrant taxi service - run from camps in Calais and Dunkirk - is believed to be netting criminal networks millions of pounds a year.

But even that is dwarfed by the money to be made by British criminals bringing migrants over by the lorry load. Jane Deith reveals how the trade is spreading along the coast of Northern Europe, to Belgium and Holland. And she hears from Europol's Chief of Staff about the extent to which criminal networks based in Britain are involved in people smuggling. He tells the programme that more than 800 people have been identified as suspects.

Reporter: Jane Deith Producer: Paul Grant.