Now for the hard work: how to launder up to £50m of cash

The main problem facing the criminals behind the UK's biggest armed robbery is how to offload up to £50m in cash - at least a million banknotes weighing 900lb - without getting caught.

With such a huge sum, the most obvious solution is to smuggle it abroad and try to launder the "dirty" money. The police have alerted Britain's ports and airports, and contacted foreign law enforcers, amid concerns that the money may have already left the country. If the criminals try to spend their haul in the UK, they are likely to be quickly identified. Financial institutions are dutybound to report any large or suspicious deposits, and much of the stolen cash is newly minted and the serial numbers have been recorded.

The cash depot in Tonbridge is one of 12 owned by Securitas - one of five firms which deliver and store cash for banks, supermarkets, travel companies and other retailers. At least £25m of the stolen cash belonged to the Bank of England, which Securitas has reimbursed.

John Horan, a money laundering specialist who works for the accountants Harbinson Mulholland, believes strict anti-fraud regulations would make it hard to move much of the money into the British economy. "You can't just walk into a bank, and businesses have to report transactions with large sums of cash," he said.

The only real option is to take the cash abroad and launder it through a front company. "They will look for countries in a state of flux, or that have poor border controls. The Balkans would be a good place to start."