The partner of Rachel Nickell is taking the Metropolitan Police to the European Court of Human Rights in a bid to get compensation.

Andre Hanscombe said he was making the claim as nobody in The Met had been held accountable for police failings after Ms Nickell was murdered in front of her two-year-old son on Wimbledon Common in 1992.

Serial sex attacker Robert Napper was finally convicted of the offence in 2008, but an Independent Police Complaints Commission (IPCC) revealed Napper - who sexually assaulted and repeatedly stabbed the 23-year-old - should have been arrested much earlier.

The report revealed Napper should have been arrested for serial sex offences known as the Green Chain rapes across south-east London in the 1980s.

Other failings, including eliminating Napper from their inquiries despite his mother telling them he had raped a woman, and not following up his failure to give a DNA sample, also allowed Napper to butcher single mum Samantha Bisset and her four-year-old daughter Jazmine at their Plumstead home 18 months later.

In a statement André Hanscombe said: "We did not feel that we could just walk away after the release of the IPCC complaint ruling earlier this year and leave things as they stood. Because no matter how damning the facts were that were confirmed publicly for the first time, it was clear that The Met had offered little to the IPCC in their investigation (virtually all the documentary evidence and corroborative files had been provided by us) and had done little to demonstrate that such an appalling catalogue of errors could never occur again.

"So many unanswered questions remained. Were we were supposed to simply accept that we would never get the answers we sought and that the police would never be held to account for the details of their grave failings? We were left in limbo all over again.

"How can it be that those affected in such a devastating way by such serious police negligence have no remedy and no process through which the police are required to fully account for themselves and remedy their actions as best as they can? Accountability is something they require of everyone else in society each and every day.

"An apology, which itself was late in coming, does not satisfy my continuing feelings of confusion and utter disbelief at the lack of professional judgement shown by those at the highest level of The Met. Those who were supposed to have had the clearest heads and best trained minds have yet to take full responsibility for mistakes that led to the death of at least three people and the suffering of many more, and the fact that we were finally told of it all too late to do anything about it.

"Alex and I have lived through the horrendous twists and turns of this case for nearly 20 years, and we are still seeking a legal remedy which will formally recognise not only the substantive police failings but also the unjust circumstances where those impacted by crime cannot hold the police liable for negligently failing to apprehend a suspect before he goes on to kill someone or for negligently conducting the subsequent investigation. Any other professional who failed to do their job so fundamentally, which such disastrous consequences, would be held to account.”

His solicitor, Kate Maynard, said: “Having learned that Rachel (and others) might not have died if the police had acted professionally and competently, André and Alex cannot fully come to terms with Rachel’s death, and move on. They are particularly concerned by the fact that those officers who so gravely failed in their duties will never have to explain themselves.

"By keeping their professional failings secret for so many years, The Met have avoided proper accountability. There is a real concern that lessons cannot be fully learned in the police service where no disciplinary action takes place and there are no formal findings in a civil court. Similar problems are more likely to occur when current officers see the officers in these cases retire and walk away from these events without suffering any consequences and when there are no Court findings against the officers concerned and their superiors. A Court award of civil damages would at least be one way of holding the officers to account.

"Since learning of these failings in December 2008, André and Alex have quite understandably been searching for what they need to do to achieve justice for Rachel. To learn that they have no legal remedy in the UK, because the police are immune from suit, even where victims have died who should have been saved, was really shocking. The police will not even recognise that their delay in revealing the truth to André and Alex was itself a breach of their human rights.

"André and Alex have therefore taken their case to the European Court, because they believe that a Court finding that the UK has violated their Convention rights will help them to feel that they have done everything they can for Rachel, that they will then be in a position to put as much of this behind them as possible and very importantly lay down a marker for others who have found and continue to find themselves in similar circumstances.”

Putney resident Colin Stagg spent 14 months behind bars before he was aquitted of Ms Nickell’s in 1994. After The Met refused to payout to the Hanscombe's he said "It makes me sick, but I’m not surprised”.