Burning Question: Just Who is Guido Fawkes' Mole?

Seems to me that Guido most likely will have got hold of these McBride emails from the recipient end of things, not from Number Ten. So which recipient's email account has been hacked and/or simply accessed by someone with server side privileges at Labour List or the like? Who is friends with GuF and inside Labour blogging circles? Or who is enemies with Draper and/or McBride and with an inside track?

UPDATE 14:48: Derek Draper offers an explanation. And the putative gossip site is online and unused. Having decided not to publish these stories did Derek pass them on to other bloggers or journalists who passed them to Guido? Or has someone unhelpful to the Draper cause got access to his email account(s)?