Did a minister have advance knowledge of the Green arrest?

This from Iain Martin over at Three Line Whip:

“…the strong rumour is that one minister with good police contacts did know [about the Green arrest in advance] and has remained well under the radar since the row erupted last week, for understandable reasons. One thought: if that person was aware of what was going on, when it backfired would they actually ‘fess up to the cabinet Secretary Gus O’Donnell, the PM or the media or just stay uncharacteristically quiet until the row blows over?”

If it does emerge that a minister had advance knowledge of the Green arrest, then it’s one of the worst things that could happen for the Government in this affair.  Rightly or wrongly, it would seriously undermine the claim that neither the PM nor the Home Secretary knew anything about it.