Legality of "mass" Christmas breath tests by Police (England)?

In this video Durham Police stop drivers leaving Newcastle Airport early in the morning for a breath test in case they have been drinking on the flight home from holiday.

At 0m 55s the police officer asks a car driver who has been directed to stop "Are you OK to give me a sample of breath?".

My understanding is that the police can only breathalyse a driver if (1) they think you’ve been drinking, (2) you’ve committed a traffic offence, or (3) you’ve been involved in a road traffic accident.

Is the fact of leaving an airport at 8am sufficient to meet Req (1) in the absence of a traffic offence or road accident, or any other indication that a particular driver may have been drinking? One officer in the video says they tested over 80 people in a single morning, which suggests it cannot be that targeted to individual motorists.

In the video example above would the driver be in any trouble if they just said "No, I am not OK to give a sample of breath"?

NB. Personally I think random breath tests like this are probably a proportionate means of reducing drink driving, but all the official gov.uk guidance seems to suggest police cannot randomly breath test (compared to the way they can request anyone's licence etc under S164 RTA).