BT SmartWater is an initiative to combat thievery of its lines by BT Openreach after rising prices, meant that BT's copper lines became more valuable than its fibre-optics.

This has led to its inherent value increasing despite the fact the telecoms' aging copper networks has no real value to the company after digital fibre-optics has replaced much of the way in which we communicate to everything from internet and TV to skype, email and facebook/twittering.

Copper, still used for fixed-line phone calls when not using mobiles is valuable as a 'soft' conductor metal which can be used in everything from electricals to plumbing and thieves of the metal - using BT's old lines - are costing the company millions of pounds in repairs each year.

Last year alone saw a nine percent rise.

Bernie Auguste, head of security at Openreach, said: "From now on, any criminal who targets the BT network risks being invisibly tagged with SmartWater, meaning that the police can trace them, and any stolen cable or equipment, back to the scene of the crime.

The criminals will be forensically 'marked' by the invisible solution - hence 'SmartWater' - which will be able to be spotted by police sixty days after any thievery.

"A search will be made of the person's house and any property, including vehicles with traces of SmartWater on them," said Detective Inspector Robin Conway of the BTP.

The BTP (British Transport Police) is to lead an investigation into stopping metal thievery including visits to scrap metal dealers to help identify criminals.

"Cable theft affects not only us as a business, but the millions of people who rely on access to phones and broadband across the UK, and with the help of this technology we're fighting back." added BT's Bernie Auguste.