To his neighbours, Peter Blackbourn was an unremarkable middle-aged man living quietly in his bungalow in Burgess Hill.

But behind the curtains of his unassuming home, was a secret "factory" running off more than £1 million of counterfeit cash from a printer in his bedroom.

Using a £5,000 Lexmark colour printer, a hot-foiler for adding metal strips and a standard home computer, Blackbourn is believed to have produced vast quantities of forged £10 and £20 notes during 1998.

His circle of conspirators included Raymond Berry, 56, of Guildford, Brian Welstead, 59, of north London, and Francis Donnelly, 48, of Watford.

Blackbourn, Berry and Welstead denied conspiracy to produce counterfeit currency while Donnelly had pleaded not guilty to possession of counterfeit currency during the trial at Hove Crown Court.

Blackbourn, a divorced father-of-two, was a computer expert who ran his own company from home, IQ Network Services.

He was also a consultant for the Ministry of Defence.

With no previous criminal convictions, his past was unremarkable until he became involved in the major counterfeit operation.

The series of fake £10 and £20 notes first came to the attention of the National Criminal Intelligence Service in July 1998.

As more than £4,000 was seized in a tiny bank in Kendal, Cumbria, and a further £6,000 came to light, NCIS traced the notes back to the home printer in Blackbourn's bedroom.

The National Crime Squad at Crawley was briefed and, just days before Christmas, officers swooped on the gang.

Detective Constable Ian Williams said: "The majority of counterfeit currency in the country at that time was attributable to that printer.

"The concerns of the Bank of England about the volume of these notes coming through was so great they desperately wanted to put an end to production.

"So our hand was forced and we co-ordinated a series of search warrants around the country at these men's addresses."

When Blackbourn's computer was seized, it was discovered part of the hard drive had been wiped off.

Mr Williams said: "He said he tried to download something which corrupted the files but our belief is by that time things were getting a bit too hot for them and they had closed the operation down and tried to destroy the evidence.

"I think it had become too time consuming for them and the printer kept breaking down because of the amount of use it was getting. It was an expensive machine and expensive to fix."

The vast quantities of notes were probably sold off round the country at a street value of about £7 for a £20 note.

The police recovered more than £40,000 but believe at least £1 million worth had been printed during 1998 with many being destroyed by the Bank of England.

Mr Williams said the production of the notes themselves was a complicated operation, with serial numbers changed individually and water marks and silver strips added.

It was only because of the unique code that each printer leaves on the paper that the officers working on Operation Neptune were able to trace the source back to the bungalow.

However, the police have no idea how much money the gang netted from their crimes as no obvious assets or sums of money were traced.

Although there was no clear ring leader, each man brought his own expertise to the operation.

For Blackbourn it was his mastery of computers and printers and for Berry it was the hot foiling machine to print the metallic strips on the notes.

Mr Williams said: "Blackbourn is a quiet man - he's not your stereotypical criminal.

"I certainly don't think he was the motivator in this conspiracy although I do think he willingly participated."

He said the only clear motive for their crimes was greed.