Stephen Lawrence’s best friend has said a multimillion-pound investigation into fears the murdered schoolboy’s killers were shielded by corruption has collapsed.

The investigation’s prime suspect, a former detective called John Davidson, has been told no evidence of corruption has been found against him.

It follows an investigation lasting nearly four years by the National Crime Agency into longstanding corruption claims in the 1993 murder case. Lawrence, 18, was stabbed to death by a racist gang, three of whom have never been convicted of the murder.

In 2014 a government-commissioned report by the barrister Mark Ellison QC said there was reason to suspect Davidson of corruption and an investigation was launched. Davidson denied the claims.

The NCA carried out the investigation, called Operation Probitas, on behalf of the police watchdog, the Independent Office for Police Conduct. It now looks set to close without making an arrest.

Duwayne Brooks, who was with Lawrence when he was killed and who survived the attack, said: “The NCA investigation has collapsed. It’s very sad.”

Brooks said he had several meetings with the NCA team and was not impressed: “I never had any confidence in them. Davidson was used as a smokescreen.”

He said the NCA team had spent nearly two years going through old police files in their corruption investigation, which Brooks said was always going to fail. “It was pointless. You are not going to find a smoking gun or someone saying in writing they have been corrupt,” he said.

Lawrence was murdered on 22 April 1993 in Eltham, south-east London, by a racist gang of at least five white youths. One of them, David Norris, escaped justice for 19 years. He was convicted of the murder in 2012 alongside Gary Dobson but three others have escaped conviction for their role in the attack.

The Guardian understands at least two senior detectives who led the Metropolitan police’s hunt for Lawrence’s killers came to fear that corruption had played a part in hampering police efforts.

Brooks said of the NCA inquiry: “It’s a slap in the face to myself and the Lawrence family and everyone who has suffered from police corruption.”

In a statement the IOPC, for whom the NCA carried out the investigation, said: “We can confirm that we have advised former DSDavidson and all interested parties that, having reviewed and tested all of the available evidence including the lines of inquiry identified by the Ellison review, we have concluded that there is no indication of corruption on the part of Mr Davidson relating to the original Stephen Lawrence murder investigation. As our investigation is still ongoing, it would not be appropriate to comment further.”

Davidson disputes the allegations. He was criticised by the 1998 Macpherson inquiry for his handling of potentially significant witnesses in the Lawrence investigation but cleared of any corrupt motive.

The NCA is continuing with a spinoff inquiry into claims of misconduct in public office against former officers involved in decision-making in the first Lawrence inquiry.

The original murder investigation was controversial because police made no arrests in the first fortnight despite being given the names of most of the suspects. Arrests were made only after Nelson Mandela highlighted the Lawrence case.

One of the suspects, Norris, was the son of a local criminal, Clifford Norris, who was alleged to have corrupt relationships with police officers.

Brooks was at one point guarded by a police officer alleged to have corrupt links with Clifford Norris.

Last April the Guardian reported claims from Clifford Norris’s family members, alleging the career criminal used a network of corrupt Metropolitan police officers to protect himself and his close relations from justice.

Ellison’s review of corruption claims was ordered by the then home secretary, Theresa May, after reports in the Guardian and Independent in 2012 about corruption. Ellison found there was reason to suspect that one officer in the Met’s first botched Lawrence investigation – Davidson – had acted corruptly.

The claims against Davidson come from his former colleague Neil Putnam, a corrupt officer turned supergrass. They were part of the “groovy gang” of detectives based at the East Dulwich office of the now disbanded south-east regional crime squad (SERCS).

The NCA investigation is expected to produce a final report about its work. It is not clear whether that, or a version, will be made public. The NCA may consider asking prosecutors to consider material.



