Do you have to stop for an unmarked police car?

Do you know what is the current law when being waved to stop by somebody in an unmarked car (presumed police)? Last week I was driving on the M4 and noticed along the way three instances of an unmarked car on the hard shoulder (with flashing blue lights by then) with cars in front that I presume they have pulled over. I believe one does not need to stop for an unmarked car. Am I right?

Asked on 15 January 2019 by Aleks Chmielewski

Answered by Honest John
You are obliged to follow the instructions of a uniformed officer and I always believed that a marked police car qualified as a 'uniformed police officer'. This is the advice of the Scottish police: "An unmarked police car can stop vehicles, but it must contain a constable who MUST be in uniform in order to carry out the stop. If a car flashing for you to pull over or stop is unmarked, unless you are 100 per cent certain it is the police, do not stop."
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