Why did 'Newsnight' apologise?

So what was that Newsnight apology about then?:

"On 7 March the Ten O'Clock News and Newsnight broadcast a report alleging a possible police cover-up over an allegedly corrupt officer, DC John Davidson. The claims should have been put to the Met, an omission for which we apologise. The Met, in fact, says that it did not claim in its evidence to the Ellison Review that there were no records of the officer's links to a separate investigation into the murder of Daniel Morgan and it does not accept that the BBC produced evidence of a possible cover-up. We were wrong to suggest the document showed we demonstrated such a cover-up and we apologise for this."

It's hard to make sense of this, but I don't think it was a specific report on Newsnight which got Newsnight into trouble. 

It seems instead to come about because of a discussion between Kirsty Wark and Mark Daly, BBC Scotland Investigations Correspondent.

That edition of Newsnight concentrated heavily on police corruption following the latest report into the way the Met had handled the Stephen Lawrence murder case. This discussion formed part of that coverage.

In 2006 the BBC had broadcast allegations about DS Davidson, and Mark Daly was involved in that report. The IPCC investigated those claims at the time, found no evidence and dismissed them. According to Mark Daly's account on the 7 March Newsnight, what happened next was that... 

The Metropolitan Police [then] launch[ed] a blistering attack on the BBC for what it called 'irresponsible and sensationalist journalism'. 

Mr Daly was bullish on that night's Newsnight, claiming that the latest report found that the Met had been misleading the public and that it hadn't handed over all the relevant documents to the investigation - in other words that there was a police cover-up after all:

Make no mistake, today's report is a vindication for the 2006 BBC journalism.

Three months later Newsnight has had to apologise again.

Oh dear.

[Incidentally, in both Newsnight's apology and the apology found on the BBC's Corrections and Clarifications page, the BBC refers to John Davidson as "DC John Davidson". He should surely be described as "DS John Davidson", as he was a Detective Sergeant with the Met.]