The new Boxster comes without even a half size spare wheel and only the dreaded aerosol can of foam to use in an emergency. I plan to drive in out of the way areas in northern Spain and Portugal and may be some distance from a source of a replacement tyre if I have a puncture.

My question is: HOW FAR CAN I SAFELY DRIVE on a tyre that has been repaired with these cans of foam assuming one drives slowly and sensibly to recognise that a tyre repaired in such a way is not suited for high speed? WHAT IS A SAFE SPEED?