Most commissioners of the Metropolitan police, once they have left the post, turn their hand to a memoir in which they seek to explain or justify their actions during their tenure of the most high-profile policing job in the country. Ian (now Lord) Blair did so with Policing Controversy. His predecessor, John (now Lord) Stevens, wrote Not For the Faint-Hearted. The late Sir Robert Mark's In the Office of Constable is a classic. Now that Sir Paul Stephenson has announced his departure, along with a few, very pointed references to the events that have led to his downfall, perhaps we can anticipate what could be a fascinating account of why the Met finds itself at the heart of the phone-hacking crisis.

Most commissioners face a crisis either internal or external that defines their tenure. For Lord Blair, it was the shooting of Jean Charles de Menezes and his subsequent handling of its circumstances. For Paul (now Lord) Condon in the 90s, it was the murder of Stephen Lawrence and the failure of the initial investigations into it. For Mark, it was police corruption – far worse than anything emerging now. For Stephenson, it was essentially his response to the phone-hacking inquiry when details of it first emerged. Had he acted swiftly when the Guardian raised the issue, he could now be calmly contemplating the policing of next year's Olympics. As it is, he has found himself the latest candidate for the high jump.

Was Stephenson right to go? Yes. He was badly advised to take on Neil Wallis, the former deputy editor of the News of the World, at a time when the newspaper's activities were already giving cause for concern. Attempts from within the Met to persuade the Guardian that the investigation into phone-hacking was excessive and unnecessary was another indication that they had not grasped the seriousness of what was happening. He was also naive in not realising that accepting hospitality from Champneys would lay himself open to criticism.

Times have changed. Sir Harold Scott was one of the Metropolitan police's most distinguished commissioners, serving from 1945 to 1953 and having the job of recreating the force in the wake of the second world war. In his 1956 memoir, Scotland Yard, he recounts how the then home secretary, Herbert Morrison, invited him to the home office. At the time, Scott was the permanent secretary of the ministry of aircraft production. Morrison's first question was: "Can you ride a horse?" At the time, riding a horse during ceremonial duties was seen as an important part of the commissioner's job. Scott said he had not ridden for a while, but was sure he would not disgrace himself in the saddle. The job was soon his.

Unfortunately, the role of commissioner has become more complex since those genial days. To lose two Met commissioners in such swift succession and under such unhappy circumstances is not just careless, but very damaging for both public and police morale. Whoever comes in now – maybe the first female commissioner? maybe someone who has already handled the complexities of Northern Ireland? – will know they will be under greater scrutiny than any of their predecessors have ever been and will have to be ready to ride a tiger rather than a horse.

Champneys, the health farm whose hospitality Stephenson unwisely accepted, offers special treatment for those suffering from "lifestyle-related health issues" and stress due to "occupation". Maybe they should produce a special package for the growing number who have been laid low by the nature of their professional connections to the phone-hacking scandal.

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