By Dominic Casciani
BBC News community affairs
The Morecambe Bay tragedy revealed the scale of illegal immigration to the UK - and its human cost. But can it actually be tackled?
Old and new: foreign earnings key to Chinese development
In June 2000, when police officers in Dover began the distressing task of removing 58 dead Chinese immigrants from the back of a tomato lorry, it was a scene they would never forget.
Fast forward to February 2004 and Britain witnessed its second major migration tragedy, the drowning of Chinese cockle pickers on the treacherous tidal sands of Morecombe Bay.
What tied the tragedies and the many, many more unnoticed immigration enforcement raids in factories, restaurants, hotels and farmers' fields is the reality of international organised immigration crime.
People-smuggling is big business and involves many different nationalities, working in different ways in different countries.
While there are 250,000 Chinese people who are a part of British society, nobody knows how many other people from the country arrived unnoticed on the back of a lorry to work in the black economy.
Demand for workers
What lies behind illegal migration from China is an interesting tale.
The number of undeclared Chinese workers is popularly thought to have begun rising in the mid-1990s.
By the 1990s, British-born Chinese had emerged as one of the top groups in schools, consistently out-performing other ethnicities and often beating white children.
They had been listening to their parents and chosen going to university over a career in catering - and that led to a sudden demand for workers in the restaurant trade to take the jobs they might otherwise have filled.
The demand for more workers coincided with the sudden opening of routes from east to west after the collapse of the Soviet Union.
58 migrants were found suffocated in the back of a lorry
Meanwhile, in China itself, a growing economy and rural poverty led communities to club together to send young men abroad to work for the common good; this in turn was very much part of an entrepreneurial, mercantile culture deeply rooted in some of China's provinces.
As a wider and more diverse range of Chinese people headed west, the opportunities they sought went beyond just working in takeaways.
Police started noticing the rise of "Snakehead" people-smuggler rackets. Far from being crude criminal enterprises, investigators came to realise that these were slick multinational networks with operations that ran like clockwork
What made the difference compared with other immigration rackets, according to some experts, is the degree of co-operation that local officials provided in developing networks which they expected would bring foreign currency back into their areas.
The individual stories of the migrants are, of course, all different. But generally, a family or community will select someone to go overseas and earn as much money as possible to send home.
Some of the cocklers who died on Morecombe Bay paid £15,000 for their passage to England. Other migrants in Britain have paid more than £30,000 to get here, with the going rate to reach the USA said to be about the same.
Passage can take up to two years in a clandestine journey overland and by air into Europe, using safe houses along the way.
Senior police officers who have studied Snakeheads say they are sufficiently business-minded to sub-contract transport to other ethnic groups (such as Turkish smugglers on the border of Asia and Europe) if it will improve the profit margin.
The key step they do control, however, is arrival. Migrants who make it are allocated jobs by "recruiters" who have identified opportunities, be they in the Chinese catering trade, sweatshop labour or picking cockles at Morecombe Bay.
But the handover to the recruiters turns the experience from a work-abroad scheme into something resembling kidnap.
Many of these undocumented migrants quickly find themselves victims of extortion, with the price of the passage hiked and threats made to the families back home.
Police officers who have raided restaurants, factories and businesses known to be using illegal workers have sometimes found up to 40 people sleeping in one room.
Subtle humiliation techniques are often used, such as denial of shoes and socks, to maintain control over the workers.
What keeps them going is the fact that their earnings play a huge role in developing their home communities: a month's pay packet in Britain can be worth more than a year's wages in poor rural communities.
While the system is simple, it is extremely difficult to smash.
Illegal immigrants rarely make contact with any authorities at all - not even the NHS - meaning they can be difficult to identify and impossible to count.
How, then, do police forces deal with a situation where they know exploitation is going on - but where nobody will come forward because they fear deportation?
Today, major police investigations tend to target rackets by treating them as major commercial enterprises - rather than regarding the immigrant as the problem.
In London's Chinatown, workers blend quietly into communities
This may sound odd, but it's based on a simple principle. People-smuggling is a business fulfilling demand in a market. If you disrupt that market, business becomes more difficult.
Techniques can include targeting weak points - money-brokers who take care of transactions between continents, hauliers who do the dirty work of transporting people and, most importantly of all, employers prepared to take on black-market labour.
But police forces are seeking to forge stronger links with communities themselves by emphasising that it is only with their help that they can attack organised crime.
Another key element in this strategy is the long-awaited Gangmaster Licensing Authority. It begins work in earnest on 6 April and will very soon have legal powers in place to target those using illegal labour. Perhaps only then will we see the true scale of the phenomenon.
All of which leaves one unanswered question: what does the government do about all these people?
The official line is apprehension and removal of illegal immigrants. But, as a committee of MPs recently pointed out, removing all failed asylum seekers alone - excluding black-market labourers - could take a decade.
Some European countries have tried amnesties for illegal workers in the hope of cracking the criminal gangs. But they also accept that individuals have put down roots and invested in the society, albeit in the twilight.
But while it means those who come forward start paying tax, there appears to be no guarantee that amnesties stop clandestine flows - and there is no sign of it appearing on the British political horizon.