A phrase originating in get medieval, 'getting Peter Harvey' on someone is extremely violently teaching them a lesson. A reference to the British teacher Peter Harvey who went balls-to-the-wall mental at a 14-year-old student who swore at him, teaching the boy a lesson he wouldn't soon forget (namely by breaking his skull with a 3 kilogram dumbell while shouting 'die die die').
Person 1: Oi, you see that idiot over there who was talking crap about me earlier?
Person 2: Yeah.
Person 1: I'm gonna get Peter Harvey on his arse.