using 3rd party ins on comp policy

[Buffalo]

my brother has a car that he isn't using at the moment and that he has just removed his insurance cover for, though it still has MOT and tax.

I have a comp policy for my own car that allows me to drive other cars, and i need to go on a round trip of about 50miles tomorrow (my car is not here for me to use).

Can i drive his car that he isn't using (it has MOT and tax) under my own comp policy, utilising the 3rd party allowance for other cars??

TIA