OK here's what happened: I used a fine screw driver and carefully removed the tail piece.

Unfortunately the locating peg was glued in place so it broke off and has remained in its slot.

No big deal, I drilled out both sides and attached a wire pin which works very well.

When I proceeded to untangle the maze of struts and tubes in the rear it turned out that other parts too are stuck really tight and look like they may also be glued. I decided to abandon the attempt and to remove the magnet from the outside rather than risk breaking more parts. The rim around the magnet was cut away by hand and then a dremel with a very fine burr was used to make one small hole just outside the edge of the magnet. The magnet is quite thin and once you get a tool around the edge at one point it pops out easily.


It's a good thing the car runs so well out of the box. I will stay with the too-powerful motor and run it on 9V.
It feels a bit strange not to be able to open it without risk of breaking it. I hope Scalextric will produce spare parts - that will probably be useful when I eventually have to take the car apart..