Who is the media's 50 quid man?

It's one of the great media mysteries of our time – even more than who still watches Peter Andre shows on ITV2. The question - just who is anonymously sending £50 notes to media types in the post? People who have received one so far include Absolute Radio breakfast DJ Christian O'Connell, Daily Mirror associate editor Kevin Maguire, BBC1 Breakfast presenter Bill Turnbull and writer and columnist Sebastian Shakespeare. Oh, and Media Monkey, who hasn't quite got around to taking it to the bank to double check it's genuine. We assume so, however, after Maguire said he donated his cash to Hope not hate. The note arrived in a plain envelope, with nothing else inside. The only (possible) clue was the Mount Pleasant postmark, a sorting office in central London near ITV and ITN and the Guardian's old home in Farringdon Road. What can it all mean?