'Hotel receipt hoarded by Margaret Fleming's killers was the smoking gun'

Iain McSporran QC believes the simple piece of paper was the pivotal find in bringing Edward Cairney, 78, and Avril Jones, 60, to justice after the carers repeatedly denied any involvement in missing Margaret's disappearance.

Mr McSporran, who orchestrated the Crown case against the evil pair, says the invoice for a stay at a London hotel, discovered within the clutter at the couple's rundown and filthy Seacroft home, was the key component in securing a guilty verdict.

The carers claimed the letter was sent by Margaret, then 19, from the Regent Palace and proved she was still alive in January 2000.

But police found an invoice within the mess at their home showing that it was in fact the couple who had stayed there at that time.

Mr McSporran said: “Without that receipt I’m not convinced there would have been a case.

“To find it was a real stroke of luck.

“Cairney and Jones were real hoarders, they did not throw anything away.

"It was an astonishing mistake to make.

"Without that I’m not convinced there would have been a prosecution."

The mystery around Margaret's disappearance is examined in new documentary Murder At My Door, which will air on the Crime+Investigation channel at 9pm on February 1.

Mr McSporran also said Cairney’s unreliable evidence in the dock helped seal the pair’s fate.

He added: “He started contradicting things he had already said. It was like nailing jelly to a wall.

“If one story didn’t turn out good, he’d just change it to another.”

The programme speaks to other key witnesses who gave evidence at the High Court trial in 2019 that ended with Cairney and Jones receiving life sentences.

The partner of Margaret's late father Derrick talks of her regret at not being able to save the tragic teenager - who she believes was killed then dumped at sea by former commercial diver Cairney.

Jean McSherry, 68, had been due to marry Derrick and wanted to bring his daughter up as her own after he died in 1995.

However, Cairney and Jones were named in his will as Margaret's carers and told Jean that the vulnerable youngster wanted 'nothing to do with her'.

She told the show: "What they [Cairney and Jones] did was evil.

"I used to wonder if Margaret would get in contact because I still had the same house phone number, but she never did.

"I thought she would have come to me if anything wasn't right but she never did, so I believed her life was good.

"I have a lot of regrets.

"Could I have done more to save Margaret?

"I really feel I let her down because I feel I never fought hard enough for her."

Cairney and Jones have repeatedly refused to tell police what they did with Margaret's body.

Jean said: "You will find her at the bottom of the sea.

"I'm still convinced of it and nothing will change my mind."

Margaret was 19 when she was last seen in December 1999, but it was not until October 2016 that a missing person investigation was launched after a benefits claim made in her name triggered routine checks.

Cairney, 78, and Jones, 60, were convicted of her murder in 2019 and sentenced to a minimum of 14 years imprisonment each.