He was shot 30 minutes after a man telephoned police anonymously and told the operator he had a gun.

Witnesses said the shooting followed an incident in which the armed man went "berserk" and fired a number of shots from the middle of the street.

Armed officers had been called to the scene and witnesses said the gunman fired several times at a policewoman in a squad car and at other motorists.

The officer who shot Mr Gillard has been taken off operational firearms duties pending an investigation.

Ballistic experts are examining a gun found at the scene.

'Fired six shots'

Peter Close, a barman at the nearby Grey Horse pub, said a man emerged from a house in Acre Road with a gun and a bottle of spirits.

He smashed the bottle in the middle of nearby Richmond Road and started shooting wildly.

No-one else is thought to have been injured in the incident.

Mr Close said the window of a police car was shot out before he fled back towards the house.

He said: "This guy was just running riot and shooting to high heaven.

"He fired a total of six shots, he shot out the police car window and the rest was frantic shooting but he didn't shoot anybody. He just went mental.

"He was just standing in the middle of the junction, in the roadway in the traffic."

Rowdy customer

Police cleared shops and homes nearby and sealed off roads.

Mr Close said the gunman had been a regular at the pub but had been barred about a month ago for being rowdy and rowing with other customers.

A Scotland Yard spokeswoman confirmed officers from the firearms unit SO19 were called to the scene after reports of the gunman on the street.

Armed response crews from the Met were called out nearly 11,000 times this year to the end of August but shots have only been fired on a handful of occasions.

Hertfordshire police are carrying out an investigation into the latest incident on behalf of the Police Complaints Authority.