The unsolved murder of a private detective is at the centre of a new inquiry
into alleged police corruption.
Officers have reopened the files on Daniel Morgan, found with an axe embedded in his skull in a South London pub car park 10 years ago.
The investigation follows an anonymous tip-off made to a new internal confidential hotline.
Detectives in the initial murder inquiry believed Mr Morgan was killed because he was about to expose police corruption.
But two officers arrested at the time later received substantial damages for wrongful arrest and false imprisonment.
The new investigation is looking at the activities of a senior police officer who is still serving and several retired detectives, some of whom held key positions while they were at Scotland Yard.
The allegations are that police officers have co-operated with prominent criminal families over the sale of stolen property, laundering of drugs money and the selling of confidential information about criminals.
They are being treated so seriously by Yard senior officers that one detective who is a key witness has been told to stay at home under surveillance for his own safety.
Locks on his house have been changed and a sophisticated alarm system linked to the nearest police station has been installed at police expense to protect him from any attempt by the underworld to silence him.
Investigators examining the allegations have also interviewed convicted drug smuggler Kevin Cressey in prison.
It was Cressey who brought down the corrupt drug squad detective John Donald, jailed for 11 years last summer.
Cressey, now serving seven years for bribing Donald, was a police informant and at one stage acted as a link between the corrupt detective and Brinks-Mat money launderer Kenneth Noye in a conspiracy involving a multi-million-pound drug-running operation.
The wide-ranging investigation is also taking a fresh look at the circumstances surrounding the suicide of Detective Constable Alan Taffy Holmes.
Holmes was an incorruptible officer who killed himself in 1987 rather than give evidence about his knowledge of bribes being offered.