A detective who caught a serial killer who dismembered his victims is hoping someone will come forward and reveal the location of their heads.

Double murderer John Sweeney died in prison at the age of 69, having never revealed the whereabouts of some of the body parts of Paula Fields, 31, and Melissa Halstead, 33.

Howard Groves, the retired Metropolitan Police officer who led the investigation into Sweeney, hopes people with information about the women’s fate will come forward now that Sweeney has died.

The 68-year-old, who retired from police work 12 years ago, said: ‘That’s one of the things I ask myself: does somebody out there know?

‘Because I suspect that someone does, other than Sweeney.

‘If they do feel they can only do it now that he’s passed away, they’re giving the family the opportunity to deal with that grief that’s still hanging over them.

‘I think it’s very difficult for us to appreciate the set of circumstances they find themselves in.

‘Your loved one has been murdered; you know all their remains haven’t been recovered.

‘You would appeal to the better nature of anybody that has got that information to come forward.’

Both Paula and Melissa were former girlfriends of Sweeney’s.

The killer threw Paula’s mutilated body into London’s Regent’s Canal in 2001.

Melissa’s body had been found in a canal in Rotterdam, the Netherlands, more than a decade prior, in 1990.

Sweeney was convicted in 2011 of murdering the women, who were both former girlfriends.

Former DCI Groves said Sweeney had been ‘arrogant’ sitting in the courtroom as the prosecution delivered its evidence.

‘He would just sit there with a pair of orange earplugs,’ he said.

‘I always remember to this day; a lot of us were sat in awe thinking, “Hang on.”

‘You are at court claiming you’re not guilty – if I was not guilty in court, I’d want to hear every single thing being said by the prosecution and the defence witnesses.

‘He sat there with the earplugs in and he was just in another world.

‘I thought to myself, “That just about sums him up – the arrogance.”

‘That was my lasting memory of him. Not somebody who showed any remorse, any regret, nothing at all.

‘I think he’s somebody who has to be in control at all times, no matter what’s happening.

‘That’s why he preyed on vulnerable women; he had to be in control.

‘He didn’t know anything else in his life but to control people.’

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