LONDON >> After months of embarrassing revelations that the police had failed to challenge dubious claims of child sexual abuse committed by prominent Britons, the head of Scotland Yard announced on Thursday that the authorities might no longer be encouraged to believe every complaint.

The officer, Bernard Hogan-Howe, who is commissioner of the Metropolitan Police, said new review of police behavior, led by a former high court judge, Richard Henriques, would be private and submitted to a current larger, independent inquiry led by a New Zealand judge, Lowell Goddard, into how all institutions handled the issue of child sexual abuse.

The new review, Hogan-Howe said, will advise police on “whether we can provide a better balance between our duty to investigate and the interests of suspects, complainants and victims.” Hogan-Howe, whose five-year contract is up for renewal, promised that “key findings” of the Henriques inquiry would be made public.

One important issue for the review, he said, was a 2014 directive from Her Majesty’s Inspectorate of Constabulary, which reviews police forces in England and Wales. It said that in cases of sexual abuse, the presumption that a victim should always be believed should be institutionalized.

But police have been too credulous, especially in the case of an informer called Nick, who made serious allegations about a child sex and murder ring involving prominent Britons around Dolphin Square, an apartment complex close to the Parliament building.

The accusations appeared to have weight when a senior police investigator briefed journalists to say that Nick and his allegations were considered “credible and true.”

In fact, they were not, and Nick has since been discredited. Hogan-Howe said the officer had “misspoken” after becoming “confused” by the need to follow guidance about complainants being believed.

The apparent confusion lasted for many months without being corrected by more senior police commanders, while further allegations were leaked to chosen members of the news media. High-profile spectacles were organized. The home of Edwin Bramall, 92, a former field marshal and head of the army, was raided, but the inquiry into him was dropped. A televised police news conference was held in front of the home of Prime Minister Edward Heath, who died in 2005.

Writing in The Guardian, Hogan-Howe said the police should be “clear about the principle of impartiality.”

He added: “A good investigator would test the accuracy of the allegations and the evidence with an open mind, supporting the complainant through the process. This is a more neutral way to begin than saying we should believe victims, and better describes our impartial mindset.”

Another former member of Parliament, Harvey Proctor, was investigated about whether he conspired with Heath to murder a child at a sex party, one of the more lurid allegations from Nick.

Leon Brittan, a former senior cabinet minister, died with unproved but publicized allegations of rape hanging over him.

The investigations followed more substantiated inquiries into abuses by prominent entertainers, many of them employed by the BBC, including entertainer Jimmy Savile, singer Rolf Harris, rock star Gary Glitter, DJ Dave Lee Travis and publicist Max Clifford. All except Savile, who died before the investigation began, were convicted of sex offenses.

Police appear to be eager to make up for past cases in which allegations that proved to be true were not taken seriously or were suppressed out of deference.

There were credible historical cases that went uninvestigated or were hushed up for years. Greville Janner, a Labour member of the House of Lords, who was alleged to have abused children, became senile and died before a court could pass judgment on his case. It emerged that the police had been ordered by political superiors not to arrest him, despite evidence suggesting he was involved in abuse, and recommendations by prosecutors for trial were rejected.

Cyril Smith, a Liberal member of Parliament, died in 2010 before serious allegations of child sexual abuse became known to the public, although a number of them had been brought to the police before he died.

Hogan-Howe acknowledged “public concern” over the conduct of the police but emphasized that “investigating historical child sexual abuse is very difficult.”

He said he would not apologize for any investigation, including the inquiry into Bramall, because investigating serious allegations is “our job.”

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