The private investigator Glenn Mulcaire is understood to have been arrested in connection with voicemail interception and perverting the course of justice.

Detectives investigating phone hacking said a 41-year-old man was arrested at an address in London on Wednesday morning and was being held in custody at a south London police station.

The man is understood to be Mulcaire, the private investigator who worked for the News of the World for several years until 2006.

Lawyers acting for Mulcaire had not responded to a request for comment at the time of publication.

The man becomes the 18th arrest as part of the Operation Weeting investigation into phone hacking. However, he is one of few to be arrested in connection with perverting the course of justice.

A police spokesman said: "At 7am officers arrested the man at an address in London on suspicion of conspiring to intercept voicemail messages, contrary to Section 1 (1) Criminal Law Act 1977, and on suspicion of perverting the course of justice contrary to common law. The man is currently in custody at a south London police station.

"It would be inappropriate to discuss any further details at this time."

Since its launch in February, the Metropolitan police's phone-hacking investigation is working its way through 300m emails from News International and other evidence.

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