A team of leak detectives from United Utilities, the water company for Northwest England, has tracked down and plugged more than 18,000 hidden pipe leaks over the past 12 months thanks to a device that has been used since the Victorian era.

The 140-strong team saved an average of 900 million litres of water –- the equivalent of 360 Olympic sized swimming pools – using wooden 'listening sticks'.

The long wooden sticks with an ear-trumpet-style end vibrate when a leak is detected, producing a distinctive sound. Used for more than 100 years, they are still a staple for modern leakage engineers.

Many of the most wasteful leaks are underground and hidden from view, requiring the team to rely on good hearing, old-fashioned know-how and the latest digital technology to find them.

Digital sensors and remotely operated pressure monitoring equipment are also used to turn the tide on hidden leaks.

Many leaks are detected late at night, when reduced traffic noise makes it easier to hear the sound of escaping water.

Hannah Wardle, United Utilities leakage manager said: "We've spotted and stopped thousands of leaks over the past 12 months, using a combination of tried and tested, old fashioned techniques, and cutting-edge technology.

"These leaks are often hidden under the streets, with no visual signs that water is being wasted. We track many of them down at night, when it's easier to hear the escaping water.”