Michael Buchanan explores the world of money laundering, and its consequences...

Early morning, and several well-dressed men with briefcases turn up at a private airfield in Florida. They board a small aircraft and within two hours they're landing on a wind-swept Caribbean island. On arrival, they're pulled over by customs officials and their bags searched. Seeing the contents, the officials quickly tell them to close their cases and move along. They take a taxi into the island's capital, visit several banks and within hours those contents - millions of illicit dollars - are safely deposited in several accounts. The "businessmen" are back in Florida in time for a sunset cocktail.

The tale may sound far-fetched, too Hollywood to be true, but it's the life that Ken Rijock lived for a decade. He started his career as a commercial and banking lawyer, but soon became a money launderer. He estimates that he helped launder at least $200 million for approximately 30 clients before finally being caught.

Quantifying the amount of money that is laundered worldwide is impossible. It is by its very nature the proceeds of criminal activity, and villains tend not to keep books

Standing near his home in the Florida Keys, he told me his rather "crude" method is still in use, but to launder large amounts of money today - say $10 million - he suggests owning a cash-rich business. "Some of the most successful restaurants in the United States have been owned by criminals because they can dump large amounts of receipts into there. Unless somebody is a very good financial investigator, they're not going to realise they couldn't possibly have that many people sitting in a restaurant over the course of a year to make those profits."

Quantifying the amount of money that is laundered worldwide is impossible. It is by its very nature the proceeds of criminal activity, and villains tend not to keep books. A conservative estimate puts the annual total in the tens of billions of dollars range, but who does it, why they do it and how it's done is constantly evolving.

Ken Rijock says he was enticed by the thrill and danger of money laundering, but for many others the motivation is simply greed. One former undercover investigator told me that some people are so desperate to get involved that they offer up family members as collateral - "If I lose your money", they tell the drug dealer, "you can kill my brother."

Money laundering is often seen as a white-collar crime, and as such is sometimes thought of as being almost victimless. But, as I discovered on a visit to Nigeria, nothing could be further from the truth. The country has suffered desperately at the hands of corrupt politicians who have stolen the country's wealth and laundered it overseas.

There is perhaps no more infamous money launderer in the world than the former dictator Sani Abacha, who stole so much money that the current Nigerian government can only estimate it to be around $3 billion. Efforts to reclaim the money have been hampered by western banking secrecy regulations, but even as the Nigerian authorities try to work their way through that mire, they are having to deal with modern-day launderers.

When I visited the country, the southern state of Bayelsa was in uproar over the conduct of its governor. He'd been charged in the UK with money laundering, but had jumped bail and returned to his state, where the Nigerian constitution guaranteed him immunity from prosecution as a serving governor. The federal government was backing calls for him to be impeached, and the head of Nigeria's Economic and Financial Crimes Commission Mallam Nuhu Ribadu told me, "We think that at this stage in our history it is fundamental that we sanitise ourselves, we must do things properly for any other thing to work. We won't be able to solve problems of poverty and disease without first and foremost getting good governance, openness and accountability.

Depending on who you talk to, money laundering started with Chinese traders 2000 years ago, or several decades ago with Al Capone's use of cash-rich businesses - like laundromats - to hide his illicit gains. Either way, the problem is well known, but it wasn't until the attacks of 11 September 2001 that concerted, coordinated international efforts began to catch the launderers.

Among the many lessons learned from that day was that without laundered money there would be no terrorism, so regulations were passed to try and stop the funding of militant activities.

The United States led the way with the passage of the Patriot Act, which ushered in new requirements on banks and other financial institutions to greatly tighten their anti-money laundering laws. Many other countries followed the US lead, introducing stricter controls on such things as foreign currency transactions and who banks can take on as customers.

...without laundered money there would be no terrorism

But, as I discovered in trawling through the costs of recent bombings - from Madrid to Bali to London - such murderous attacks have now become so cheap that many experts believe it will be almost impossible to choke off their funding.

Douglas Greenburg, a lawyer who has studied the financing of the 9/11 plot, says: "If you have someone who is working, depositing their pay cheques into the bank and periodically withdrawing money and, at night, buying components for a bomb, what's the bank going to do about that?"

So, despite all the new policies and protocols, money laundering will continue - to motivate crime, undermine economies and finance terrorism - all at the same time. Hardly the definition of a victimless crime.