The smugglers, organised along similar lines to the infamous Triad gangs, will typically produce photographs of happy Chinese families outside large houses with expensive cars in the drive.

''You too could enjoy such a lifestyle in a couple of years," they tell them.

Often a whole village will club together to pay for one person's passage in the hope that some of the wealth will be sent back.

Torture

Many of the migrants come from Fujian province in east China.

Police believe the smuggling routes pass through Russia and into western Europe via Hungary or the Czech or Slovak republics.

Migrants are promised fabulous riches in the West

Goods lorries provide the hiding place for the ferry crossing to the UK from mainland Europe.

But the gruelling and doubtless terrifying journey is frequently only the start of the nightmare.

Once in Britain they may be kidnapped and taken to safe houses, where they are told they will be killed if their families do not cough up hefty ransoms.

In a recent case in London, the distraught relatives back in China were made to listen to their loved ones screaming down the phone as their kidnappers beat them with the flat sides of machetes.

Often the gangs will steal batches of illegal immigrants from each other in a bid to discredit their rivals and carve themselves a larger slice of the smuggling trade back in Fujian province.

Typically the hostages will be handcuffed, not fed properly and generally abused.

Handcuffed

The problem has become so severe that Chinese police are now helping British detectives crack down on the trade

Last year 19 gangsters were locked up for a total of 200 years following a series of police operations resulting in the release of 50 people. Most of the victims were kept in awful conditions.

Most illegal immigrants enter Britain by ferry

Police came across one hostage who had his finger sliced to the bone when he refused to rape a female captive and another who was getting just one bowl of gruel every other day.

Another shocking case came to light when police found a terrified Chinese man wandering in a daze in a street in south-east London. In grave fear of his life, he had escaped his captors by jumping bare foot through a first floor window.

When officers raided the flat they discovered another four hostages. One had been held for more than 22 months. He had been repeatedly assaulted and treated like a slave. When not working he was kept handcuffed.

Ransoms

But police say they came across the worst abuse at a west London flat where they rescued five hostages who were being tortured for ransoms of 250,000 yuan ($30,700) each.

The smugglers hide their human cargo in lorries

When kidnappers realised the family of one of the captives would never be able to raise the cash, they told the other four they would be made to draw lots and the loser would have to kill the one who could not pay.

Although there have been no confirmed links between killings and kidnappers, two Fujianese were found chopped up in bags in east London in 1995. The murder has never been solved, but the evidence suggested a gangland execution.

Global industry

Detectives at Scotland Yard's Organised Crime Group fear the cases they come across are just the tip of the iceberg. Many victims do not come forward for fear of retribution by the gangsters or deportation back to China.

Around seven to 10 gangs are thought to control the trade from China to Britain. But they are just part of a global industry in people smuggling that is worth an estimated $4bn a year.

Many of these gangsters - or snakeheads as they are known - are thought to have been previously involved in the drugs trade but switched to people trafficking because of the high rewards and relatively low penalties if they get caught.