A gipsy mob trashed a £5million police helicopter – to stop officers spying on them.

They set about the Surrey force's chopper with axes – putting it out of action by smashing five windows.

The attack followed weeks of aerial surveillance on a travellers' site where swish stolen cars and nicked goods are believed to be stashed.

A police source said last night: "The gipsies were furious because they kept getting buzzed by the helicopter.

The mob struck at 10pm after leaping over a 4ft wall surrounding the force's helipad at Fairoaks airport, near Woking.

They threatened staff in the operations room before wrecking the chopper.

The damage caused was estimated at tens of thousands of pounds.

The aircraft, which is expected to be out of action for another two weeks while repairs are made, is the only cop chopper in Surrey.

The neighbouring Met and Sussex forces are having to provide air cover for the county's one million residents.

Detectives were ready to raid the gipsies' site on the back of evidence filmed from the air.

The source said: "We suspect it is being used to store expensive stolen cars and other goods. Before a raid is conducted we will observe the criminals from the air.

"That way we get an idea what we are likely to find, identify suspects and locate entrances and exits. Maybe we got too low."

Security at Fairoaks is being beefed up following the attack.

The helicopter was airborne 214 times during April – an average of seven flights per day.It is mainly used for chasing crime suspects and their cars, finding missing persons and pre-planned surveillance operations.

A camera fitted under its nose beams broadcast-quality footage to the control room.

In just 12 minutes, the copter can search an area that would otherwise take 450 man-hours.

A Surrey Police spokesman described the identity of the mob members as "unknown".

He said: "The incident is part of an ongoing investigation and security measures are being reviewed as part of this.

"We are working with a maintenance contractor to ensure the aircraft is back on line as soon as possible."