SCOTLAND Yard spent more than £8,000 carrying out post-mortem examinations on the suspected victims of the so-called Croydon cat killer.
The force's three-year probe was closed earlier this year after officers released a report, in which they said foxes were responsible for mutilating the animals.
Pet owners had feared a serial killer was on the loose after hundreds of cats were reported to have been decapitated and dismembered across the south London borough and beyond since November 2015.
There were also reports of similar incidents in Southampton - sparking fears that the alleged cat killer had begun targeting other cities.
However, in September this year, the Metropolitan Police said there was "no evidence that any of the cats had been killed by a human".
The force has now revealed it spent £8,100 on post-mortem examinations during the probe, codenamed Operation Takahe, in response to a freedom of information request.
In response, Scotland Yard said assigning officers to work on the investigation as a whole was much more efficient than having individuals on each case.
The figure includes: £6,000 on post-mortem examinations in 2016; £800 on a re-examination of post-mortem examinations in 2018, which the Met said was the cost of the laboratory only, with no charge for the pathologist's time; and £1,300 on microscopic hair testing in 2018.
However, the total amount spent over the three-year investigation was not revealed, as Scotland Yard said there was no "cost code" designated for Operation Takahe, making it impossible to calculate spending on officers, staff and other expenses.
However, the Met estimated 2,250 police hours were spent on the probe, with two detectives and two constables on the investigation team at one stage.
Frontline Policing Commander Amanda Pearson said: "The decision was made to allocate a large number of similar reports of mutilated cats to the officers who were investigating the initial spate of such allegations in Croydon. In particular, they were following up six suspicious cases identified by post-mortem examinations.
"While this increased the workload of those officers, it significantly reduced the resources that would have been required for different officers in different units to record and assess each allegation separately.
"It is this collating of reports that enabled officers to work with experts and reach the conclusion that no further police investigations are required into any of the allegations relating to mutilated cats."
The mystery had baffled locals, and Croydon-educated actor Martin Clunes was among those to weigh in when he wrote a letter to detectives in February 2016.
"I read with horror that some of the cats had been decapitated and dismembered - this is the stuff of nightmares," he wrote.
"The local community is understandably distraught and frightened. No-one feels safe while this sick individual is on the loose."
Police ruled out the theory that "a person or persons were travelling the county and mutilating animals on a serial basis", and said all of the cases of cat mutilation will be recorded as "no crime".
The Met said the post-mortem examinations on an initial 25 cats found they succumbed to a blunt force trauma, such as being run over.
Their bodies were said to have been mutilated after death.
Six cases were deemed to be suspicious and required further investigation, during which another 400 reports of cat mutilations were collated in and around London.
A Scotland Yard statement in September said: "The investigation took almost three years, due to the number of reports and allegations received from the public and the need to work with specialists to scrutinise any evidence.
"No evidence of human involvement was found in any of the reported cases. There were no witnesses, no identifiable patterns and no forensic leads that pointed to human involvement. Witness statements were taken, but no suspect was identified."
In three cases, CCTV footage showed foxes carrying cats' lifeless bodies in their jaws.
The Met said it "took note of expert opinion" which highlighted how wildlife can be known to scavenge on roadkill, often removing limbs before dumping the corpse.
Chief Inspector Stuart Orton, who led the investigation in Hertfordshire, added: "The evidence suggests that the animals had been predated by foxes - in a rabbit's case after being removed from a hutch, and in a cat's case after death, likely caused by a road traffic collision.
"I hope this conclusion brings comfort to pet owners who have, up until now, been frightened to let their animals out at night."
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