The events leading up to Andrew Mitchell's resignation from the Cabinet in October are now even more blurred, complex and highly charged than they were at the time.

Although the Prime Minister knew before his Chief Whip left the Government that some of the police evidence against the cabinet minister was not reliable, he neither said so publicly at the time nor moved from his balanced position between Mr Mitchell and the police.

David Cameron had been ready to sack Mr Mitchell, but was struck by the vehemence of his denials and ordered internal inquiries, parts of which appeared to challenge officers' accounts of the fracas at the gates of Downing Street. Yet Mr Cameron offered no public explanation – apparently because he did not want to poison relations between the Government and the senior officers who protect them, but more likely because of the existing stand-off with the police over deeply unpopular reforms.

The result was a bizarre sequence of events in which Mr Mitchell protested his innocence somewhat vaguely, without clarifying precisely whether or not he had accused officers of being "plebs"; the police were insistent that Mitchell was not telling the truth; and the Prime Minister floated uneasily between the two. In the end, Mr Mitchell resigned, although, given how strongly he is fighting back now, it is something of a mystery why he did not cling on more tenaciously in the first place.

With cause to doubt the police evidence, Mr Cameron should, perhaps, have acted more decisively in defence of the beleaguered minister. But even if he were not himself sure enough of events to give his full backing to Mr Mitchell, at the very least he should have ensured that the questions over the police accounts were made public and swiftly investigated.

Instead, Mr Cameron opted for the most political of solutions, a behind-the-scenes deal designed to smooth over the public row and minimise the risk to himself and his Government. Indeed, he allowed expediency to trump any concern over the facts of the matter, despite the far-reaching implications of their uncertainty. Even as the police face questions following the latest twist in the tale, so too does the Prime Minister.