Assistant Commissioner David Veness, said CCTV cameras in parts of the airport were not as good as those in some high streets.

Mr Venness, head of Specialist Operations at Scotland Yard said he had "grave concerns" over security after two major robberies in supposedly secure parts of Heathrow.

Mr Venness said it was wrong to distinguish between non-terrorist crime and terrorism, because a weakness in one security area showed a weakness in another.

Millions of dollars in cash was taken in a security van raid at the airport on Tuesday, which followed a robbery in February.

'Effective regime'

It is thought both heists may have been inside jobs with the raiders using legitimate security passes.

Many companies working at the airport provide their employees, some temporary, with passes.

The firms are currently responsible for carrying out security checks on them.

Mr Venness said: "We are very keen that the airside pass regime should be as effective as it conceivably can be and that CCTV is as good at Heathrow as it is in many high streets in London."

In the latest raid $3.2m (�2.25m) was being transferred to a van after arriving on a South African Airlines flight from Johannesburg.

Two men forced the driver to drive at knifepoint to nearby Cranford where the money was transferred to another van.