IT was hailed as an innovative plan to catch burglars, but the secret behind a Police Scotland operation to spray people's valuables with an invisible anti-crime liquid can now be revealed.

The single force last year trumpeted a sting which led to officers catching a thief who stole a planted bike coated with the solution in Edinburgh.

However, Police Scotland has now confirmed there was another factor behind the crime being detected: an electronic tracking device attached to the bicycle.

The force launched a pilot in early 2014 with London-based SmartWater Technology in a bid to deal with a rise in housebreakings in Edinburgh.

Around 600 homes in the Grange and Greenbank areas were given a special liquid product to brush on their belongings.

A stolen item could then be identified under ultra-violet light and the culprit would, in theory, have the solution on his clothing and hands if they had handled the goods.

Stories were given to the local press about the pilot, Police Scotland praised the initiative, and the force linked a fall in housebreakings to the project.

Assistant chief constable Wayne Mawson credited the pilot with having a "dramatic" effect on reducing crime and described the SmartWater product as having a "fantastic proven track record".

The project was rolled out nationally to 4,500 homes in Pollokshields and Rutherglen in the west of Scotland, Killearn and Blanefield in Stirlingshire, Torry in Aberdeen, Longniddry and Gullane in East Lothian, and the Duddingston area of Edinburgh.

However, the link between the SmartWater technology and the fall in crime may now be questioned.

The company and the force last year revealed details of how a man was arrested and charged following an incident relating to the liquid

A bike marked by the liquid was placed by the force at a location in the capital and, once it was stolen, officers located the property to an address in the city.

The suspect was arrested after allegedly being found covered in the solution.

However, both the police and SmartWater press releases failed to mention that a secret tracker had also been fitted to the bike.

A SmartWater case study of the partnership with Police Scotland, which is on the company website, later stated: "To maximise awareness, a high profile campaign was developed to drip feed SmartWater-related news stories to the local press.

"To further target the criminal fraternity a covert 'trap-bike' marked with SmartWater and fitted with a tracking system was deployed at various locations across Edinburgh."

It is understood the tracker was a SmartWater product.

According to Police Scotland, the Edinburgh pilot resulted in a 53% fall in domestic housebreaking in the relevant locations.

However, the force said a freedom of information request would be required to get the actual figures behind the reduction.

A Police Scotland spokesperson said: "Police Scotland brought in the SmartWater technology to prevent housebreakings in target areas. After a successful pilot in Edinburgh the scheme was rolled out across Scotland at a cost of £60,000. The money spent covered the cost of training officers, marking kits, specialised torches and signage. Specialised torches were also provided to some second hand dealers - they can check property in their shops to ensure they're not selling stolen goods."