AN unmarked police car came in useful when officers inside were able to witness dangerous driving on the M4. 

Police saw a white van driver was seen exceeding the 70mph speed limit and driving recklessly while on a patrol of the motorway on Sunday afternoon. 

Wiltshire Police posted about the incident on its Wiltshire Specialist Ops Twitter page, dedicated to roads policing and armed response activity and shared a video that had been captured of the suspect vehicle in question. 

The post said: "Unmarked car came in useful this afternoon when we witnessed this white van exceeding the speed limit and inside overtaking several vehicles on the M4 between junction 18 - 17."

Video from the police car shows the van swing from the outside lane to the inside lane, speeding past traffic by 'inside overtaking' and then moving back into the middle lane. 

The video also shows the unmarked car acting to keep up with the van, and that it was going at 90mph in order to do so. 

Since being posted, the Wiltshire Specialist Ops account has deleted the tweet.