I'm not saying, but mine is not a 'works-prepared' car - I prepared it all myself for historic rallying.
One of the problems is that most of those criticising what is done these days were not around and building/preparing Minis in the '60's.
Let me give you an example. I had a friend who was a BMC dealer and a rally driver. In fact I navigated on several events with him in his 1071 'S' and sometimes he drove my 1964 998 Cooper. Now he had a customer who had an almost new 850 which had a shunt up the back. As it was only about 5 months old the insurance company instructed him to buy & fit a brand new shell. This he did and he retained all the original numbers which is what the insurers wanted to avoid devaluing the car. Now he had a fairly good and totally rust-free but slightly damaged Mk.1 shell and it was simple to do the rear end repair. So this shell was used to re-shell his 1071 'S' after he hit a tree 'big time' on the International Tulip Rally. It also retained the original numbers and was painted gold/black as his 1071 had always been. To everyone it was just the same car, but nicely repaired and just as strong.
In those days this was not unusual and I had an apprentice working with me who had an early 850 Mini. This was in 1968. He rolled it, but we were working in the design offices of an aircraft company who also owned a BMC dealership next door (in Cambridge). I knew their bodyshop manager and he found a similar shell which had been replaced on a 1967 car. The apprentice bought this shell as a special 'inside the company' deal and re-built his 850 into it. It was still a '62 car, technically, but it had a bigger rear window and rectangular rear lights.
This sort of thing was commonplace and no-one thought anything about it. Is there some sort of theoretical 'cut-off' point at which a car ceases to be 'genuine' if it has been re-shelled? The body-shell was just another part number in the parts book. The number of rally car crashes, in Minis and other cars, which have resulted in the owner saying not to worry as he has a 'couple of spare shell' in the workshop is huge and we all did it 'back then'. Now folk are getting paranoid about it. Using the no re-shelling criteria, virtually all the 'works' rally Minis are 'ringers'.
I had a 998 Cooper in 1968 into which I fitted an 1275 'S' engine and gearbox, a 120 mph speedo, twin tanks, etc, and it's mechanical specification was that of a Cooper 'S'. I sent the log-book to the Ministry of Transport (before DVLA days), told them the engine was a 1275 'S' gave them the engine number and the log-book came back as a 1965 1275 Mini Cooper 'S', colour red/white. Everyone jus said it was a Cooper 'S'.
But times change and attitudes as well. Those who were not there don't understand all this. That's not their fault, but they don't see things the same way as we did when the Mini was a new car.