Further to my earlier posting - sadly I was unable to get the seized security bolt off by the suggested means of whacking on an undersized socket. Even a friendly AA patrolman couldn’t manage it although he did bash off the fragile outer bolt head – which was actually helpful.
I was told by a local welding specialist that trying to weld a nut onto the bolt head risked damaging the alloy wheel. A couple of local tyre specialist garages reckoned they could do the job but would not commit themselves on price. In the end I settled on a retired gent (75 years old!) recommended by a local tyre fitter as a mobile specialist. He came to my home with his equipment and true to his word got the bolt off by drilling it out. Took him half an hour.
Watching him do the job he started out with a small bit and gradually progressed until he was using a chunky one. Having eventually made a suitable sized hole (about 13mm wide and 10mm in depth) he then used a nifty precision snap-on socket. This was roundish at one end with a bolt head at the other end onto which you put a standard socket. Then he banged these combined parts in forcing the roundish end into the hole. Then out came the bolt as easy as you like using a long bar.
On the basis of this exercise I would say that a competent DIY mechanic could do this job provided he has the necessary variety of tough high-quality drill bits and, crucially, either owns or has access to this particular unique snap-on tool/socket. They come in a set and apparently cost about £80 plus VAT which I know is a lot especially if (like me) you probably won't use them again. One final point – drill slowly!
Security wheel bolt knackered - postscript
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