I would think it highly unlikely. I've never yet known where permission has been granted to knock holes in the walls of listed buildings. But why, with all those outbuildings at their disposal, would they have needed to build a garage?
Some places have garages with a door which leads into the kitchen. No need to " knock holes " anywhere. There could have been a lean-to,we don't know.
You'd better ask the relatives because it was RWB who'd mentioned a back door in the garage with a bolt/bolts bashed off it along with a smashed lock.
I just wondered if it led into the kitchen via a door and not a " hole ".