A man who ran a gun-conversion factory from his living room was among a criminal gang jailed for a total of 43 years.

Gary Waller ran a cottage industry turning harmless imitation handguns into lethal weapons from his South Norwood home.

The 30-year-old was part of a six-strong gang of gunrunners, middlemen, purchasers and criminals uncovered by a five-month investigation by Scotland Yard’s Trident unit in 2008.

Officers discovered Waller had built a basic but extremely effective conversion factory in a living room cupboard and recovered six firearms when they raided his home in Seymour Villas.

These included a converted and loaded Magnum, Glock, Steyr machine pistol and two Brocock Olympic .38s, and another Magnum in the process of being converted.

Waller pleaded guilty to a string of firearms offences due to overwhelming evidence, and was sentenced to 10 years imprisonment at Croydon Crown Court yesterday.

His gang included 19-year-old Darren Yaw Okupu from New Addington, who acted as a courier delivering weapons to “customers”.

During Opoku’s trial the judge dismissed the indictment of possession with intent to enable another to endanger life on the grounds that there was no clear evidence of the defendants' intentions.

Prosecution counsel Chris Coltart successfully had this decision overturned by the Court of Appeal.

Detective Constable Phil Carruth from Trident said: “Hopefully these lengthy prison terms given to the six individuals today will act as a deterrent to others who choose to be involved in the conversion use and supply of firearms throughout London and the Home Counties.

“The success of this case and similar being undertaken by Trident's proactive teams continues to show the dedication and commitment of officers to target these dangerous individuals.”

The other gang members:

-Marvin Welch, 29, of 12 Mirfield Court, Selby Road, South Norwood was used by Waller to store finished and partly finished firearms in his flat, located close to Waller's home.

-Wesley Huggins, 25, of 3 Henry House, Wyvil Road, Vauxhall and Adrian McNeish, 27, of 27A Grove Vale, East Dulwich. Both acted as middlemen sourcing customers and using “runners” as couriers to deliver the converted weapons.

-Cadele Clarke, 25, of 1 Beauclerk House, Leigham Avenue, Streatham, a criminal who bought weapons from Waller.