A man has captured footage that appears to show a Mercedes travelling at up to 120mph on the A11 near Attleborough.

The driver, who recorded the images on a dash cam in his vehicle, said he called 999 on his hands-free phone when he was overtaken on the northbound carriageway at around 4.45pm yesterday by the silver Mercedes.

The man, speaking anonymously, said he had analysed the footage when he got home to estimate the vehicle's speed.

He estimated it was between 110mph and 120mph, based on GPS data and the time it took the car to travel the distance to the bridge in the video.

He said: 'It's absolutely ridiculous. So many people are getting killed on roads nowadays - I've lost people I know - and nothing is done about it.

'It's crazy, and I wish people would campaign to stop this.

'It's so sad, and it's needless.

'I've got kids and family and I do 1,000 miles per week in my job.

'I want them to know I will get home safely.'

He added that drivers should think of the consequences if a vehicle pulled out in front of them while travelling at that speed.

This newspaper has passed the footage of the incident to Norfolk police.

Chief Inspector Chris Spinks, head of Norfolk and Suffolk's roads policing unit, said: 'Norfolk Constabulary received a call at 4.47pm yesterday from a member of the public stating they had seen a silver Mercedes car travelling at excessive speed on the A11 at Attleborough.

'Officers on patrol in the nearby area were given the partial details of the vehicle provided however it was not located.

'The constabulary has since received YouTube footage of the alleged incident however it is not possible to identify the vehicle or driver.

'It is not appropriate for us to comment on this particular incident as we have only been provided a brief snap shot of the footage and do not know the full circumstances.

'There is an increasing use of dash cams by drivers and this footage in certain circumstances can be vital in our enquiries particularly when investigating serious or fatal collisions; however, due to evidential requirements it is not always possible to proceed with many of the recordings where evidence of more minor incidents have been captured.

'It is necessary to be able to prove date, time and location of the offence as well as tracing the driver of the vehicle.

'It could also be necessary for the person providing the recording to have to attend court to produce the footage.

'However, should members of the public record events leading up to or actually showing a collision, we would ask them to hold on to that footage and respond to any witness appeal we may make in relation to that particular incident.'

It comes as Norfolk and Suffolk police launch a crackdown on speeding drivers after recording motorists travelling at up to 114mph on Norfolk's roads.