Can anyone help explain what was going on here?

Today I was driving near High Wycombe. A Thames Valley police car was behind me for a minute or so. As I came to a complicated set of mini-roundabouts, it turned on its blue lights and set off its siren, forcing me to pull over in a dangerous section of road between the roundabouts.

A policeman came over, bent down by the window and asked in the chummiest of tones: “Are you having a good day?" I said I was until he showed up.

He asked if my name was Jonathan Cook. He then asked what I was doing here. I responded that I was visiting family. Was that a problem?

He answered that it was routine to make checks on what he called “cross-border activity”. When I asked him what he meant by “cross-border activity”, he said the car was registered to an address in Bristol, and that was a two and a half hour drive away – it’s not, it’s 1 hour 45 minutes away. He added that it was a long way to come.

I must have looked slightly stunned. He told me not to worry, wished me well and – with a smile – said I could continue on my way.

Have others had a similar experience? Is it now normal to be stopped in the UK simply because you’re driving more than 90 minutes from home?