This is the dramatic moment a lorry is caught on camera shunting a car side-on 100 metres along the M25 at 50mph. But the accident was caused by the hesitancy of the car driver who failed to join the motorway lane correctly.

The haulier could have been looking at an expensive insurance claim from the Honda Civic’s driver after the collision. A Smart Witness camera had been fitted to the lorry's dashboard which conclusively proved the car driver was to blame.

Gary Humphreys, Group Underwriting Director for Markerstudy Group, said: "These cameras are a cheap and effective device to help innocent motorists and we expect they will become more commonplace.

"Camera technology adds a visual element in helping insurers decide fault in the event of an accident, as well as providing individuals with evidence following road rage incidents or dangerous driving.

"We have had claims for incidents on roundabouts and over lane discipline where the camera has proved vital in determining liability and has enabled us to avoid long drawn out disputes."

He added that having a camera fitted can reduce premiums by up to 20 per cent. 

Smart Witness managing director Simon Marsh said: "Drivers worry blame will always be attached to them when they hit another vehicle from the rear, particularly when there are no reliable witnesses.

"In this case, the lorry driver was very relieved his Smart Witness camera meant he could quickly prove the accident was not his fault. This latest video shows the risk which all motorists face on a daily basis and how efficient a Smart Witness camera is at revealing the truth.

"Thankfully in this case, no insurance claim was filed but who knows what could have happened if the camera had not been there."

Smart Witness systems have saved insurers £20million by providing evidence against fake whiplash and personal injury claims. Figures released by the insurance industry earlier this year showed up to 60 per cent of the 550,000 whiplash claims filed each year were bogus.

Experts said claims had soared because people were 'motivated' by the ease of claiming in financially tough times. Sales of Smart Witness accident cameras have soared by 40 per cent in the last year as motorists protect themselves against the dangers of fraudsters.

Mr Humphreys added the cameras help protect drivers against the scams which have now become a £1 billion industry. He said: "The cameras can help protect drivers against 'cash for crash' scenarios. This includes deliberate severe braking in front of a driver to instigate a 'slam on' and subsequent whiplash injury claims.

"They can also guard against 'flash for cash' claims where a driver flashes to let another out of a junction and then crashes into them on purpose."

The cameras, a bit like a black box journey recorder, fit onto the windscreen, are powered through the car's cigarette lighter or can be directly wired in. They record the driver's view of the road ahead and also monitor the car's location, speed, breaking and impact G-forces.