The BBC is on astonishingly biased form today.
At about the same time as Marr was making his onslaught against David Cameron, Radio 4's Broadcasting House was broadcasting a gentle interview with a Baroness Glenys Kinnock (scoring an meagre I.C. of 0.2 - and the one interruption wasn't much of an interruption). Presenter Paddy O'Connell praised her for "all (her) experience" and allowed her to make a silly, self-contradictory attack on David Cameron without comment and said "that's a fair question to ask" about another attack on William Hague.
This was followed by a piece on Old Etonians in the Tory Party. You could have guaranteed that someone at the Biased Beeb would have brought up the subject. Labour, most notoriously in the Crewe by-election, loves to bring up this issue. Marr having brought up the subject the Bullingdon Club and, thus covered the Oxford angle, it was therefore up to O'Connell to bring up Eton. He discussed it with Nick Cohen of the Observer (naturally) and the unaffiliated Professor Byron Criddle.