Who is Patrick (Mac) MacDowell from The Eye in the Door and what is their importance?

Patrick MacDowell is one of Billy Prior's childhood friends from Salford. Mac's mother, Lizzie, was a heavy drinker and a known prostitute. For much of his childhood, Mac was severely neglected by his mother. Consequently, Mac was eventually taken in by Beattie Roper. Mac's sentiments against the war lead to his being on the run from the authorities. As a conscientious objector, Mac faces prison time if he is caught.