Hmm, that slow puncture of mine...
I normally only use my car at the weekends, and the tyre was taking the best part of a week to lose its air, so for the past few weeks I'd been pumping it up to full pressure at home before using the car each weekend, and then keeping it topped up with the garage airline each day I used it, thus getting what I thought was normal usage. Don't ask me why, but I have an aversion to using the space-saver spare, and I was reluctant to get the puncture repaired because I mistakenly thought it would mean leaving the car with someone for half a day or longer.
Then, prompted by markjay's report of a super-quick while-u-wait repair, I sought out a (better-equipped) tyre place last weekend who said they could offer the same quick service. However, when they saw the tyre, their faces dropped. What I had taken to be kerb-rubbing on the sidewall of the nearside rear tyre (I've been a little careless with my parallel parking of late

) turned out to be heat damage from running the tyre while it was gradually losing air (even though I considered it to be fully inflated). The image below shows the damage to the nearside tyre, compared to the offside tyre that was fitted at the same time less than a year ago.
This was a sobering moment for me, even moreso when they took the tyre off and revealed a multitude of "rubber filings" from the inner sidewall nestling within the carcass. Oh dear. They obviously declared it irreparable; unfortunately they didn't have any matching ContiSportContact 3s in stock but said they could get a pair in within a couple of days, and gave me a price for them. I asked if they could put the old tyre back on the car so that I could at least get it home; the guy was quite reluctant to do so, but said there was no real danger of it self-destructing provided I kept it inflated, used it as little as possible, avoided doing more than 30-40mph and got it changed within a week or so.
He needn't have worried, as I wasn't going to take any risks with it - the car went straight home and stayed put, while I did a quick check on blackcircles.com. Surprise, surprise, they were able to do two MB-spec ContiSportContact 3s including balancing and fitting at one of their premier centres for almost £100 less than the other place had quoted me.
So, as of this afternoon my car has two new rear tyres. Of course, I should have done this in the first place, and if I'd realised how silly it was to keep running a tyre with a slow puncture, it would have been changed/repaired as soon as the tyre alert had first come on. Just goes to show you're never too old to learn a valulable lesson...
The culprit: