A gang of businessmen, including two from Birmingham, have been jailed after laundering more than £15m from NatWest.

The high street giant was tricked out of the money after others discovered a "flaw in the banking system".

They found that following its takeover by the Royal Bank of Scotland, they could pay in worthless cheques and then withdraw the money before they bounced. The cash was then "cleaned up" with the help of several mobile phone and IT companies and a number of bogus business deals. Scores of equally fictitious documents were created to give the transactions a false gloss of legitimacy.

By the time the "very simple" fraud was discovered, most of the missing money was in Latvia. But the account it was sent to was quickly frozen, preventing it being wired on to a "safe haven" in Dubai.

The remaining £1.5m was siphoned off en-route and split between the money launderers and the thieves, who pocketed up to £125,000 each in the process.

London's Southwark Crown Court heard that fortunately police in Riga, Latvia - which had recently signed up to EU money laundering controls - realised something was amiss and tipped off their UK colleagues.

Those before the court - current and former directors of firms in London and Birmingham, Airdrie and Glasgow, were all convicted of conspiring to launder the money between January 1 and July 31, 2004. All insisted they were innocent dupes and had been conned by those who masterminded the scam.

The Birmingham defendants cannot be named for legal reasons. The other four are Tahir Butt, 28, of Braemar Avenue, Wimbledon, south-west London, and Mohammad Hamid, 28, of Morton Road, Morton, south-east London, who ran IT Players in nearby Fulham, and were each jailed for four years, three months. Ilyas Anwar, 35, of Barrhead Road, Glasgow, who headed a company called BHS in Airdrie, got a similar sentence, while Syed Alam, 51, of nearby Barrhead Street, who was a former director of a Glaswegian company called Starmack, received two years.

One of the two Birmingham men was also jailed for four years, three months, while the other was sentenced to two years and nine months.

They, Hamid, Butt and Anwar were also found guilty of plotting to produce false instruments - the numerous documents used to make the fraud look legitimate - but cleared of conspiracy to defraud the bank.