can he put weight on his leg and walk a short distance in a specific time (if asked by a police officer if he was in an accident?) did your insurance specifically say it was ok?
I was told by our insurance I wasn't covered while my left leg was in a cast (driving automatic) as I couldn't put any weight on my leg. there is a section in the Highway Code about being able to walk x length in under x time to demonstrate you are in full control of your vehicle, etc. but I can't find the link.
I live on a private estate and we all own the roads. I have always assumed you could drive around here without a licence (although it would not be wise as if you hit someone you'd have to pay and also the car insurance of the insured person almost certainly will say only the named drivers (who presumably all have licences) are the only ones allowed to drive the car).
You cannot be prosecuted for driving without a licence if you drive in a supermarket car park as it is not a proper road. You can, however, be prosecuted for driving without insurance. The supermarket may also be unhappy with people driving without a licence on their land.
The law is a strange and mysterious land, and as such, sometimes defines the words it uses - in which case it's the "legal" definition which matters as opposed to the "normal" definition.
(The reverse is also true. If a law uses words it doesn't define, then courts have to use the "accepted" usage, rather than a specific usage).
With regards to driving, "Private" has a very narrow meaning. From memory (I once knew) it's land which the public CANNOT access, except by crossing a barrier. This is very important, as it's a fundamental factor in the offence of drink driving ... you can still be prosecuted if you're drunk on a public highway - which includes a highway the public could have accessed, despite being privately owned.