Took the car in for service and MOT last year. The garage who do the service (and who I have no reason to distrust) take it elsewhere for the MOT.
It passed but with the advisory "Both rear tyres cracking".
Garage chap and me went out to look for these cracks and eventually spotted what I'd call microscopic surface crazing to some parts of the sidewall. The garage chap didn't think it was a problem. I've taken some photos to upload but you just can't see the "cracks".
I dutifully check the tread and the pressure every month and have been watching the "cracks" which look exactly the same now as they did then.
MOT is due Friday, and I'm planning to take it to the same garage. Can this be reason to fail MOT? The car does average mileage and I'd expect the tyres will be changed in the next 12-18 months due to tread depth.