The compact Royce was recently taken for its biannual test of 'roadworthiness'.
It passed OK, but with a recommendation that I change the front tyres on account of uneven wear.
I'd already noticed that if left to its own devices, the car would pull to the right, and I'd wondered if the tyre baldness had anything to do with it.
With new tyres fitted, the car now drives in a perfectly straight line, so the answer to my question was resolved; it was definitely the tyre.
All four tyres had been replaced about 2 years ago, so they were all of the same age, and same type. Why just one should wear so badly I don't know. Maybe the culprit was just badly made. I notice that it was worn on both the inside and outside.
I usually change my tyres every 2 or 3 years, whether they need it or not. I don't do a great milage so it's enough.
Above are the two actual tyres in question; one can clearly see the difference.