Background: Catalogue of police misconduct over supergrass Karl Chapman

Susie Labinjoh also criticised the failure to discipline or charge any officers involved despite a series of investigations and judgments detailing a catalogue of improper inducements which were concealed from prosecutors and the courts.

Ms Labinjoh, who sued the force on behalf of Gary Ford after the majority of his convictions for robbery and burglary were quashed, said: “The conduct of the officers in this case was utterly reprehensible and it is shocking that still, not a single individual has been held to account for their actions.”

The scale of wrongdoing surrounding the treatment of Chapman in the mid to late 1990s first emerged when the Supreme Court issued withering criticism in a judgment published in 2011 which detailed the reasons for quashing the murder convictions of Paul Maxwell and Daniel Mansell.

Lord Brown, one of five law lords cited in the judgment, described the findings of the Criminal Cases Review Commission (CCRC), which referred both the Ford and Maxwell and Mansell convictions to the Court of Appeal, as “not just disturbing but quite frankly astonishing.”

He added: “They reveal that, as a result of his cooperation with the police, Chapman and other members of his family received a variety of benefits which were not merely undisclosed to the CPS (Crown Prosecution Service) or counsel but were from first to last carefully concealed from them.

“They were benefits which both contravened the controls designed to preserve the integrity of Chapman’s evidence and were in addition inherently improper.

“Amongst the more surprising were that whilst in police custody Chapman was at various times permitted to visit a brothel, to engage in sexual relations with a woman police constable, to visit public houses, to consume not merely alcohol but also cannabis and even heroin, to socialise at police officers’ homes, to enjoy unsupervised periods of freedom, and indeed, throughout the actual period of the appellant’s trial, whilst threatening not to give evidence after all, he was permitted long periods of leisure (hours at a time) in places of his choice, ostensibly as “exercise”, and in addition phone calls and visits from his own solicitor.”

The CPS decided, in both 2005 and 2006, that there was insufficient evidence to bring charges after receiving files on 18 officers from North Yorkshire Police, who carried out a lengthy investigation on behalf of the CCRC into the allegations.

The CPS upheld its original decision after fresh representations were made by Mr Mansell’s solicitor in 2013, in the wake of an investigation carried out by The Yorkshire Post, further detailing the police wrongdoing and how it had been investigated.

The Supreme Court judgement, which included incredulity that not one single officer had either been charged or disciplined, prompted a fresh inquiry by West Yorkshire Police into its decision not to discipline any officers and whether any evidence existed for fresh misconduct action.

But it was concluded no officers had faced action because it was considered unfair for more junior officers to be disciplined when senior officers had been able to retire and because of the time-lapse between the misconduct and when disciplinary files were received in 2006.

The police’s treatment of Chapman took place in an era when using a ‘supergrass’ had become fashionable and when clear-up rates were of increasing concern to police forces with a keen eye on crime statistics.

He was arrested in 1994 and quickly signalled his intent to co-operate with police on a range of alleged crimes.

As well as access to drink and drugs and overly familiar relationships with officers, extra favours included an allegation of rape and a charge of wounding being dropped.