Watford residents have been warned about a scam where door-knocking conmen ask for cash payments for nationally-funded gas works.

The National Grid, which is carrying mains replacement work across the town, said a man dressed in a suit visited a property in an area of Watford where it had been working on Monday July 30.

The resident was then asked to pay for the gas mains work, which had just been completed, but refused.

However, the resident did allow the man to check his boiler.

Kevin Blundell, Operations Manager of the North London Gas Alliance said: "The public is not charged directly for our gas mains replacement work and any work, repairs or reinstatement associated with it.

"If they are asked for money this request should be refused and the matter reported to the police and ourselves as soon as possible."

"All National Grid and North London Gas Alliance employees carry official identity cards which they should show to people before entering their property.

"People should not let anyone in if an official identity card is not available for inspection."

Anyone with information about suspicious door-to-door visits is asked to call the police on the non-emergency telephone number 101.