Two carers have been convicted of murdering a 19-year-old woman whose death they covered up for 20 years and whose body has never been found.

Edward Cairney, 77, and Avril Jones, 59, killed Margaret Fleming in December 1999 or January of the following year.

The authorities only became suspicious in October 2016 when concerns were raised about a benefits claim made by Jones on Ms Fleming's behalf.

A huge police search operation has failed to find any trace of Ms Fleming.

Cairney insisted during the trial at the High Court in Glasgow that Ms Fleming is still alive and had gone to London.

He claimed that she regularly returned to their home in Inverkip, Inverclyde, when she needed money.

He also claimed Ms Fleming, who had learning difficulties and went to live with the couple after her father's death in 1995, fled out of the back door when police first arrived to search the house, known as Seacroft, for her.

But a jury found Cairney and Jones guilty of murder after a seven-week trial.

Jones was also found guilty of fraudulently claiming £182,000 in benefits by pretending that Ms Fleming was alive.

Lord Matthews, the trial judge, said he would pass sentence after social work and medical reports were compiled on the pair.

The last independent sighting of Ms Fleming was when Jones' brother Richard saw her on 17 December 1999.

She did not join the rest of the family for Christmas dinner the following week. On 5 January of the following year Jones told her mother that Margaret had ran off with travellers.

There have been no sightings of her since, and detectives were unable to establish how she died or what happened to her body.

Cairney and Jones tried to cover their tracks by travelling to London, and letters purporting to be from Ms Fleming were posted to their home in a bid to cover up their crime.

Bogus diary and calendar entries were also written to suggest Ms Fleming had left the house voluntarily.

Despite this her benefits continued to be paid into Jones' account, without challenge, for more than a decade.

The trial heard that a benefits investigator attempted to visit Ms Fleming in June 2012 but was told by Jones that she would not see her.

The investigator said a duty social worker should have visited the "totally chaotic" property to follow up on the young woman's welfare, but no-one did.

When police were finally alerted four years later it was as a result of a missed appointment and an application form for Personal Independence Payments (PIP) - which had been filled out by Jones.

In it she wrote that Ms Fleming "needs constant care", had self harmed and was "caught eating out of a dog bowl".

A social worker phoned Jones to offer help and was told Ms Fleming had not been to the doctor, despite picking a hole in her head.

Police Scotland subsequently launched a missing persons' investigation in October 2016 but an extensive search of the house - which included two downstairs bedrooms full of rubbish - and its grounds failed to uncover any trace of the teenager.