Five men received sentences of between three and eight years for their attempt. Through an insider at the bank, the gang attempted to make 21 money transfers over the financial network Swift, moving the money to a number of recipient accounts based in Turkey, the United Arab Emirates, Israel, Hong Kong and Singapore. But, due to a mistake in the messages the transactions were unsuccessful and no money was transferred.

The investigation unravelled the "complex web" of companies and accounts which had been set up to launder money, as well as catch the "insider" and two other members of the gang who had escaped arrest, through circulating CCTV footage in Europe.

Soca says about £1.5m in assets was restrained and will be the subject of further action under the Proceeds of Crime Act.

Soca's annual report also revealed it completed a major overhaul to its IT systems to improve data handling and meet operational requirements.

"In June 2008 Soca established its information management programme, under which the planned IT improvements for 2008/09 were delivered to time and budget, ensuring that all staff who needed it had appropriate access to Soca's core operational systems, and that the necessary in-year investments in systems and processes for Soca's longer-term effectiveness were made," it says.