When police raided the operation, which had an array of hi-tech equipment, the gang had already distributed hundreds of fake �50 notes.

A stack of notes, with a face value of just under �689,350 was also found at their headquarters.

London's Southwark Crown Court heard they could have printed about �1.5m a fortnight, which would have flooded Britain with fake notes in months.

The notes were of a very high quality and were the best seen by the Bank of England for some time. Detective Inspector Kevin Vanterpool

Gary Pollard, 45, of Castlehaven Road, Kentish Town, north London, who was regarded as a central figure in the organisation, was jailed for four-and-a-half years after admitting possessing counterfeit notes with the intention of distributing them and possessing articles or items used in their manufacture.

Printer Anthony Hogg, 50, of Delawyk Crescent, Herne Hill, south-east London, got three-and-a-half years after admitting the same two charges.

Maria Yianni, 30, of Holloway Road, Archway, north London, who was caught with �405,000 worth in a holdall, pleaded guilty to possessing counterfeit notes and received two-and-a-half years.

After the case Detective Inspector Kevin Vanterpool, of the National Crime Squad, said: "The notes were of a very high quality and were the best seen by the Bank of England for some time.

"The arrests and convictions have prevented any further distribution and successfully disrupted an organised crime group that had potential to have a significant effect on the economy."

'Financial influence'

The court heard the counterfeiting came to light when an undercover officer posed as a buyer and infiltrated the gang.

Ken Millet, prosecuting, said the officer met Pollard and Yianni in a bar and secretly recorded the pair negotiating the supply of an "immediate substantial quantity of counterfeit �50 notes, followed by a similar amount in about six days' time and thereafter on a regular and projected basis".

"It became clear from the recorded conversations that Yianni had not some little input and that Pollard had control and a direct financial influence over a counterfeiting operation.

"It also became plain that it was intended that the proceeds from the transaction they were about to undertake were to be invested in obtaining a more efficient machine which would be able to permit faster production and enable the supply of 30,000 notes a fortnight with a face value of �1.5m."

'Serious matter'

They meet later that day at the Grafton Hotel in Tottenham Court Road, central London, to handover �500,000 in fake notes.

Yianni was arrested after she pushed a bag under a table so the undercover officer could inspect its contents.

Other officers searched Hogg's home and found counterfeiter's equipment, including a hot foil printing machine, a scanning machine, negatives and printing plates.

Passing sentence, Judge Paul Dodgson told the trio: "If this had not been nipped in the bud, I have no doubt millions of pounds worth of counterfeit notes would have found their way on to the streets. This is a very serious matter."