text: We've learned a lot about the end of the journey, the slave camps and mass graves in the jungles of Thailand and Malaysia.
  What we haven't heard so much about is how these journeys begin.
  We travelled to southern Bangladesh, where many of the migrants set off on their perilous voyages.
  What we have discovered brings a shocking new dimension to this story that speaks of the terrible desperation that is driving this vast movement of people.
  We met one of the people smugglers on what Bangladeshis proudly boast is the world's longest beach - a vast stretch of sand that runs for more than 120km along the southern coast.
  Let's call him Kamrul Rahman.
  He appeared to be in his early 30s.  He said he used to be a fisherman and started in the people smuggling racket greedy for money after his business went belly up.
  As the surf crashed down on the beach beside us, he calmly explained in chilling detail how the business worked.
  He said the prison camps were an essential part of the business model and all the migrants knew about them.
  It seems they are part of what amounts to a sinister and hideously cynical marketing trick the people smugglers have evolved: they offer the voyage for virtually no upfront cost.
  He said the deal was straightforward and understood by everyone involved. You only pay the main charge - about Â£1,500 ($2,300) when you arrive in southern Thailand.
  I was amazed. "So the migrants know they will be held in camp before they get to Malaysia?" I asked.
  "Before they leave from here we tell them if they don't pay they will be put in a prison. You won't get any rice and you will die of hunger", he told me, without any sign of emotion.
  "If you pay, you will be able to start for Malaysia with honour."
  We spoke to many migrants and relatives of migrants in southern Bangladesh.
  They all confirmed his account. Without exception, they said they knew migrants would be held in Thailand until full payment was made.
  What this suggests is that for the most part this phenomenon isn't strictly human trafficking - where people are bought and sold against their will - but rather a perverted business transaction to which most of the migrants and their families are actually party.
  The so-called "ransoms" migrants who have been rescued from the camps in Thailand say their captors are actually part of the deal they sign up to when they make the journey.
  Take a moment now to think about what that tells us about the people who make these journeys.
  They are so desperate for a better life that they are willing to go with the people smugglers even though they know that they may end up starving to death in a jungle prison camp.
  Stina Ljungdell, the UN refugee agency representative in Bangladesh, agrees that many migrants do know what they are getting into.
  If you think about it objectively, it makes a kind of sick business sense for both the smugglers and their customers.
  The migrants are assured that they only pay the full cost if they actually arrive in Thailand - cash on delivery, if you like.
  Meanwhile, the smugglers have leverage to guarantee that they get paid.
  The model has the added advantage, from the perspective of the smugglers at least, of making the decision to attempt the trip much easier.
  It seems many young men, and it is predominantly young men who seem to make the journey, are lured in the risky and selfish hope that their family will find a way raise the money once they arrive in Thailand.
  But other migrants make the decision to leave together with their families, judging that it is the only way to lift them out of poverty.
  We were told that a successful migrant can send as much as 30,000 taka (Â£260/$400) back to his family each month.
  But many, many migrants don't make it.
  Within minutes of arriving in an unofficial camp for Rohingya refugees further up the coast, I was surrounded by parents showing me pictures of their missing sons (and occasionally daughters).
  Some said their sons had left for Malaysia without telling them. Many others, however, said they had sent them off in the hope that they would send money back for the family.
  According to the smuggler, one in five of the migrants he takes don't make it to Malaysia.
  Many die before they even reach the camps, he told me.
  "Some die because of the suffering, some die because of of tension, some die thinking about how to escape from the situation and some people die of hunger after they run out of food.
  "All people have to die", he said, "that is fate."
target: Over the last couple of weeks, the world has woken up to the horrific trade in human beings being conducted in the seas of South East Asia.