We haven't learned much about the private life of Harry Pearce, who's in charge of the 'Spooks' at 'MI-5', save that he's divorced and that he has a grown daughter from whom he's estranged.
But what if we look back along his family lineage? Who was his father?
I think it just may be pozz'ble that his biological father also worked in the British intelligence community. It could be that his father was named Villiers and he worked for Sir Charles Portland. His code name was PR-12. (That bit of information was supplied by 'The Prisoner' while in the body of the Colonel.) Just an idea....