The Westminster terror outrage came at a time when the Metropolitan Police is without a permanent Commissioner in charge.
Sir Bernard Hogan-Howe, who led the force for five and a half years, retired last month.
But extraordinarily there is still no date for when his successor, Cressida Dick will take over.
Deputy Commissioner, Craig Mackey, has been in temporary charge of Scotland Yard in the interim.
But he was unable to lead the terrorist investigation in the initial stages because he was being treated as a “significant witness”, having watched events unfold.
It is understood Mr Mackey had been in Westminster on official business when Khalid Masood launched his bloody rampage which left three innocent people, including one police officer dead.
He had been just about to leave in his unmarked car when Masood sprinted through the gates, which had been opened in order to let his vehicle out.
Mr Mackey was then swiftly whisked away by his protection team who took him straight to New Scotland Yard, which is now just yards away on the Embankment, having moved from its previous location, last year.
Mr Mackey, who was the Chief Constable of Cumbria Police in 2010, when gunman Derrick Bird went on the rampage, was finally able to take full charge yesterday morning, once he had given a statement to his officers.
But there has been questions around the lengthy gap in permanent leadership between Sir Bernard’s retirement and Ms Dick taking up the reigns as Britain’s top police officer.
It is understood the delay in Ms Dick starting her new job is simply because she has been required to serve out her notice at her current post at the Foreign and Commonwealth Office, where she has been working since her retirement from the Met in 2014.
A source said had been keen to begin as soon as possible but had responsibilities to fulfill at the FCO before she could move.
It is understood the notice period has been significant reduced anyway.
An announcement on what day she will take up her new post is expected to be announced by the Mayor of London in the coming days, but she is not expected to start for around another month.
Met sources insisted there was no concern about the apparent lack of leadership because Mr Mackey had the full confidence of everyone associated with Scotland Yard in his capacity of acting Commissioner.
Asked about why Ms Dick had not taken up her new role immediately, London Mayor, Sadiq Khan said: “Like most people who are successful in their jobs, they have to give notice to their current employer.
“You’ll appreciate the job she does with the Foreign Office. She’s got to make sure she serves out her notice – it has been reduced.
“She’s already been doing lots of work. Even though she’s not begun being paid, that shows how professional she is.”
A source said Ms Dick had been at Scotland Yard just hours of the attack and was being kept fully up to date with all the developments in the investigation.
But LBC Radio presenter Nick Ferrari told his listeners: “It just doesn't sit right, does it in this situation.”
He went on: “It seems truly extraordinary. You would not allow this to happen in a business, would you?
“If you're running a major business the size of this you decided the chief executive is off or he decided or she decided, you would put the chief executive in the next afternoon, wouldn't you? But not so the police, who are in charge of our security.”
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- Sadiq Khan
- Cressida Dick
- Parliament shooting
- London attack
- Metropolitan Police Service
- Khalid Masood
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