Phone hacking scandal: Who is next in line?

London Mayor Boris Johnson wears a policeman's hat in Trafalgar Square

Yates of the Yard looks to be next in line for the Boris treatment.

The Mayor of London has just signalled that he expects the Professional Standards Sub Committee of the Metropolitan Police Authority to investigate the Met's Assistant Commissioner John Yates.

It is responsible for "Senior Officer Conduct" and its tasks include "to investigate and deal with any allegations, report and complaints about the conduct of officers of ACPO rank in accordance with appropriate regulations".

If he is investigated it will not be for failing to re-open the enquiry into hacking but for his relationship with Neil Wallis, the News of the World's former deputy editor who was hired to offer the Met PR advice.

Yates may be tempted to point out that at the time some argued that the hacking row was "codswallop" and "a politically motivated put-up job by the Labour Party".

To be more precise those were the words of the Mayor of London, Boris Johnson.

Update 0936 BST: Assistant Commissioner John Yates was the man tasked with carrying out "due diligence" before the Metropolitan Police awarded a contract to the firm run by Neil Wallis, the former Deputy Editor of the News of the World in September 2009.

I understand that Yates received categorial assurances from Wallis that nothing would emerge that would embarrass either of them or the commissioner.

The Met took the view that Wallis had never been "in the frame" over phone hacking - a view that only changed more than a year later when News International revealed new information at the beginning of this year.

This led to the arrest of Wallis, his former boss Andy Coulson, Rebekah Brooks and others.

If the Metropolitan Police Authority do launch an inquiry into Yates this morning it will not be the first inquiry that he - or, indeed, many senior officers - have faced.

They are routinely launched in response to complaints about the behaviour of senior officers and do not normally require the officer to be suspended.

Yates, I'm told, has no intention of resigning and would only do so if his judgement is found wanting by the official inquiry led by Judge Leveson.

Along with other senior officers he is said to be angered by what one source described as a "political maelstrom which is casting careers aside at whim" and the current "trial by media".

Yates has complained to colleagues that he was harangued and shouted down by MPs on the Home Affairs Select Committee last week and that no-one is focussing on the facts - in particular, that his decision not to re-open the phone hacking investigation was backed by the Crown Prosecution Service and leading counsel.