An invisible spray of almost indelible water could eclipse burglar alarms and CCTV as the leading protection against theft from property.

SmartWater International makes the claim after its forensic fingerprinting device eradicated crime from one of the worst-hit schools in Buckinghamshire.

Forensic fingerprinting is a system whereby secret screens are placed around premises.

When intruders pass through these screens, a detector is activated, releasing a low-pressure sprinkler, spraying droplets over the intruder.

The droplets, which the company says are harmless, act as a synthetic forensic fingerprint. They are almost impossible to detect in normal light and very difficult to remove.

Police can subject a suspect to ultra violet light which will show immediately whether they have passed through a secret screen.

Before SmartWater's system was installed, the Meadfurlong school in Milton Keynes suffered 36 break-ins in one year.

Since Meadfurlong was equipped with forensic fingerprinting in 1996, it has not suffered a single break-in.

“Criminals have the greatest respect for the power of forensic science,” said Philip Cleary who is joint managing director of SmartWater.

“Experience shows that where Index Solutions warning signs are on display, very few intruders will take on the challenge.”

The system carries Home Office approval.