At just four inches long, it fits easily in the hand and could be a key fob of the type used to open car doors by remote control.

But this tiny device is in fact a lethal weapon - a gun capable of firing two 0.25-inch bullets.

Yesterday, a thug was jailed for nine years for using one like it to shoot a man for 'disrespecting' him in a nightclub.

Marcus Henry's weapon was converted from a pocket gun designed to fire miniature flares, a gadget which is legal in Bulgaria where they cost £15.

Around 100 are believed to have filtered into Britain from Eastern Europe in the latest worrying illustration of how weapons once found in the realm of spy fiction are falling into the hands of criminals.

The double-barrelled gun is fired by pressing buttons on the side.

Henry, 27, shot Yaw Darko Kwakye from nine feet outside the Departure Lounge club in the City of London on December 16 last year, hitting him in the shoulder.

Mr Darko Kwakye survived because, due to the short barrel of the weapon, the bullet did not fire straight but rotated through the air and hit him side-on. Henry was jailed at the Old Bailey yesterday.

Mark Heywood, prosecuting, told the jury: 'In these days of heightened security, particularly in our capital city, if someone wants to carry a weapon it must be concealed.

'One method of concealment is to disguise what it is - a remote control key fob of the kind you might find is used to open the doors of a car.'

The court heard that Henry, who was in the club with a friend, had been seen chatting to Mr Darko Kwakye's girlfriend shortly before the club closed at 4am.

Mr Heywood told jurors that after a fight between the two men in the club, Henry lay in wait outside when the club shut and confronted members of 24-year-old Mr Darko Kwakye's group.

'Henry was seen to have his hand near his waistband on a number of occasions and was heard to say, "Look how many of you there are, there's only two of us",' Mr Heywood said.

'He then brought his hand out and into a straight-arm firing position and then aimed in the direction of Mr Darko Kwakye and the others.

'There was a lot of movement and between two and four sounds like shots.'

The victim's group at first scattered but then returned to smash the windows of Henry's car as he sped away.

'Mr Darko Kwakye had in fact been hit in the right shoulder, but he didn't realise it,' said Mr Heywood.

'He went down the street and got into a car with two others. He realised as he was travelling away there was blood on his shirt and a bullet hole.'

The gun was found hidden in a sock with traces of Henry's blood on it during a police search of a house.

Henry, of Battersea, South-West London, denied he was the gunman, but was convicted of possessing a firearm with intent to endanger life, possession of a prohibited weapon and unlawful wounding. He was acquitted of attempted murder.

Jailing him, Judge Christopher Moss said the offence of bringing a loaded firearm into a public place and using it should meet with a 'severe prison sentence'.

Mr Heywood asked for the gun to be forfeited but not destroyed, so that the 'novel weapon' could be used for training purposes by the police.

Detective Sergeant Dave Carter, of City of London Police, said: 'They are very dangerous weapons, arguably more dangerous than your average handgun because to the casual glance they look like something different.

'It is not particularly accurate but from a short distance it can be fatal.'

Three years ago in Manchester, suspected gang member Fabian Flowers, 19, fatally shot himself in the head while demonstrating a similar gun in a nightclub.