I really think a statement about his medically acknowledged paranoia is the trump card here – I can’t see Motability taking action which will either prevent the car being used, or effectively force the car to be used in a way which is directly opposite to the rules.
PLEASE note, I said the statement would be the trump card, not the condition…
"Man is born in freedom, but he soon becomes a slave, in cages of convention, from the cradle, to the grave."