Two guns disguised as pens have been seized in raids at the homes of a pair of teenage gang members.
The weapons were recovered from the homes of two young men in Waltham Forest, east London, today.
Members of the Met's Territorial Support Group arrested the suspects on suspicion of possessing a firearm and ammunition.
A 16-year-old was arrested at a house in Orange Grove, Leytonstone, and a 17-year-old was held in Higham Street, Walthamstow.
The older boy was also held on drugs offences after suspected class A drugs were found and handling stolen goods.
The raids, code-named Operation Cinnamon, were launched after police found a pen gun wrapped in a sock after splitting up a gang on the street last November.
Several different types of pen guns are available in the United States, but only one design is legal because it looks like a pistol.
There are numerous guides to converting pens into one-shot shotgun-style weapons on the internet.
In November 2009, a man was jailed at Manchester Crown Court after drunkenly trying to sell a home-made James Bond-style fountain pen gun to a stranger in a car.
The Met's private so-called "Black Museum", housed in New Scotland Yard, contains several different pen guns kept to help police officers recognise them.
Waltham Forest borough commander Chief Superintendent Steve Wisbey said: "Today's operation is designed to clamp-down on gang activity in the borough.
"Our intelligence exposed gang members involved in firearms. We've arrested two people for a serious crime, but this is not a one-off.
"Our gang programme that we've launched is an ongoing commitment to tackling these types of issues.
"We're giving gang members an opportunity to change their ways with help and support via the programme.
"If they don't want to change and continue to commit acts of criminality they will feel the full force of the law.
"I would like the public to know the Metropolitan Police Service are committed to tackling gang-related crime.
"There are a lot of ongoing operations around youth violence that we are working on 24/7."
* Two young men remained in custody at an east London police station tonight.