I'm astonished by this.
Previously, there was guidance that the exercise should be for at least as long as the journey. So no driving 2 hours for a 10 minute walk.
Driving 5 miles, or 7 miles if that takes about 20 minutes and they walk for an hour (with their tea to help stay warm) would have been within the guidelines.
As many posters have said, they have to travel further for their supermarket.
If it was a popular tourist spot and hundreds were flocking there, causing issues with parking and inability to social distance, then the Police would certainly be in the right to move them along.
A wide, empty space for 2 of them to take a walk, not so much.
Power crazed.