Motorists are being warned about a ‘friendly gesture’ on the road that can land you in hot water, as it’s actually illegal.

With an estimated 150,000 drivers caught speeding each year and rates rising, it's no surprise that some motorists like to warn others about a mobile police speed check van up ahead, and flashing headlights is a common way to do this.

However, UK motorists are being warned they could face fines of up to £1,000 if they are caught doing this.

Other habits that could land drivers in hot water include beeping their horn in anger or pulling over to use their phone with the engine still running.

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Gordon Inglis, a driving expert at The Car Buying Group, explained: "Flashing your headlights to warn other drivers about a mobile speed camera van might seem like a harmless and kind gesture, but it could land you in trouble.

“Police use mobile speed vans to make roads safer. They are in place to check vehicle speeds and issue fines to those breaking the limit, helping to deter speeding.

“If you are caught warning others of a speed van ahead, not only are you breaching The Highway Code, but the law also considers this as ‘obstructing police duties.’

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“Under section 89 of the Police Act 1997, it is an offence to intentionally prevent police from doing their job. If caught, you could face a fine of up to £1,000.

"While it may seem like you’re helping a fellow motorist, you could also be aiding reckless drivers in avoiding detection.

“Speed limits exist to keep everyone safe, and enforcement helps to deter dangerous driving and catch drivers that pose a risk on the road. 

“Stick to the speed limit and let others take responsibility for their own driving. A quick flash might seem helpful, but it’s not worth the risk."