A driver has warned speed cameras on the M25 could catch drivers out even during quieter times of the day.

Tom Tompkins, who is a regular user of the M25 in the Watford and Rickmansworth area, recently has noticed the anti-clockwise mandatory speed warning set at 50mph between J18 and J17.

He says traffic on both occasions has been light during the afternoons and the gantries with speed warnings before and immediately after show nothing on them.

He explained: “This one section of motorway between Chorleywood and Maple Cross has in both directions speed cameras that appear in the top ten of the highest revenue fine collections in the country.

“Could it be that many of these fines are the Highways authority way of generating revenue from motorists by simply switching on one mandatory speed gantry.

“Seeing this happen now on more than one occasion makes me very suspicious of the motives for just one active mandatory speed sign.”

A Highways England spokesperson advised that speed limits are not necessarily 50mph, they may be 60, 50 or 40, or sometimes even lower in exceptional circumstances.

They added that the reasons for using reduced speed limits are widespread such as traffic congestion and road-worker safety.

They said: “We want drivers to be able to use motorways that are more reliable, safe and keep traffic moving, so smart motorways use variable mandatory speed limits to tackle frustrating stop-start congestion and to improve safety.

“Speed enforcement cameras are used on smart motorways to improve speed compliance in order to achieve these outcomes.

“Highways England receives no revenue from enforcement cameras, however they play a valuable role in enhancing safety, smoothing traffic flow and reducing congestion for millions of motorists who use our roads.“