When Sir Paul Stephenson took over at Scotland Yard at the end of January he promised a new approach to policing the capital. There was to be a clean break with the Ian Blair years – even though he had been the Deputy Commissioner throughout that period.

Just a couple of months into his tenure, however, questions are already being asked about whether he has, or can get, a grip on the most important policing job in the country.

The latest disasters to befall Sir Paul are the death of Ian Tomlinson, minutes after he was assaulted by a riot-helmeted officer, and the demise of Bob Quick, his counterterrorism chief, who made an elementary mistake that may have compromised a major security operation. To the outsider, the Metropolitan Police looks indisciplined, disorganised, arrogant and incompetent.

Sir Paul started the job with tough talk, speaking of a return to basic policing values, a strong uniformed presence on the streets and bobbies who would be in touch with local communities.

Since then, there has been a steady stream of disasters that give the impression that the top brass at Scotland Yard are seriously out of touch with the men and women who patrol the streets.

Sir Paul announced that he would be returning to single officers walking the beat then, on the same day, he marched 80 officers to the home of a suspected burglary gang leader. They battered down the door only to find that the suspect had already been arrested in the early hours of the morning (by a couple of officers). No one had bothered to tell the top man.

On the morning that he was to address a conference marking the 10th anniversary of the Macpherson Report into the death of the black teenager Stephen Lawrence, Sir Paul was forced to rewrite his speech after it was revealed that an Asian officer was taking the Met to an employment tribunal over allegations of an "apartheid" culture at Belgravia police station.

Sir Paul admitted to the existence of "pockets of stupidity" within his force as the tribunal heard that racist bullies at Belgravia had a "black van/white van" system for officers of different ethnic backgrounds.

Next up was the staggering incompetence displayed in the investigations into two serial sex attackers. The convictions of John Worboys and Kirk Reid led to revelations that Met officers on supposedly specialist units investigating rape and sex offences had dismissed women's reports of being attacked and failed to follow compelling evidence that would have removed dangerous predators from the streets. Apologies followed and moves are now afoot to reform the investigation of serious sexual assaults.

Then came G20, and more tough talking from the senior command at the Yard. The officers leading the public order operation spoke ominously of dangerous elements planning violent protests; one said the Met were "up for it" and the message percolated down through the ranks, with constables writing on internet forums that they were preparing to take on "the scum of society".

Despite heavy criticism of the penning in of 5,000 people – the vast majority of them peaceful demonstrators – around the Bank of England on April 1, officers robustly defended their tactics. Mr Tomlinson was said to have died of natural causes. Despite possessing a massive amount of video footage from the streets the police did not admit to concerns over his death until they were forced to do so by the emergence of amateur film given to the media. Only then did Sir Paul say that an investigation into the death was necessary.

Now the Commissioner has lost one of his most senior officers, albeit one with whom he has had a strained relationship since the arrest last year of the Tory frontbencher Damian Green.

Sir Paul has turned to John Yates, the man the Yard always seems to call on when things get rocky, to try to steady the ship. But the pressure is on the Commissioner to get back on course quickly. He must prove that his force is not racist, will listen to victims and can act with discipline and responsibility.

He must do that quickly because the man who announced Bob Quick's resignation this morning, Boris Johnson, the Mayor of London, is developing a habit of shedding senior coppers.

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