Just to add confusion to the debate. My VVC has an Avon spare wheel in the boot which has been there since March 1977. It is the only remaining tyre from when the car was built and has never touched the road. It is therefore effectly a New 33 year old tyre which is not cracked or split but it is date coded. But I would never dream of actually using it because of its age, so VVC also has a spare on the boot lid which is a great deal younger in age, just in case I ever need to change a tyre.
Now I have spoken to our local traffic cops and our MOT man and both said that the condition of the spare is not a subject for the MOT and therefore can not be cause to fail an MOT. Also our local traffic cops added that it only becomes an offense when you fit the spare [or if they want to be awkward with you, if you intend to fit the spare]. The problem is, once on the road with a defective spare wheel in the boot, how do you prove that you are not intending to fit it?
Anyway, the low mileage 2000SC has got its original set of tyres in place and they look good for their age (39 years) but I must admit I would be very dubious about taking her far on them. I certainly wouldn't consider anything above 50mph, which incidentally is the top speed which most space savers are rated at. Incidentally, again talking to our local boys in blue, if the speed rating of a space saver is 50mph and you are doing 70mph, you are more than likely going to get a ticket so beware!
Anyway, the law says:-
You are not, required to carry a spare. Nor does it have to satisfy all the tyre condition rules if you do have one – but if it is used, it must then pass all the laws relating to the other tyres such as tread depth (1.6mm), condition and use. This includes suitability of construction, load and speed ratings as well as pressures suitable for the total vehicle weight.
Space savers should only be considered to be suitable if supplied as original equipment.