A couple who tortured and killed their nanny before burning her body on a bonfire in their garden have lost a Court of Appeal challenge.

Sabrina Kouider, 36, and her partner Ouissem Medouni, 41, killed 21-year-old Sophie Lionnet over an entirely false belief she was having an affair and colluding with ex-Boyzone singer Mark Walton.

The pair were jailed for life and ordered to serve at least 30 years behind bars at the Old Bailey in June 2018 after being found guilty of murder.

They each challenged their minimum terms at a hearing in London, while Medouni also launched a bid to appeal against his conviction, but their cases were dismissed by senior judges.

The Old Bailey heard Kouider's delusional disorder triggered her false belief Ms Lionnet had been seduced into helping Mr Walton to commit abuse.

In reality, Ms Lionnet had never even met the music mogul - a founding member of Boyzone who had once been in a relationship with Kouider.

Over more than eight hours of recorded interrogations, the au pair was slapped, likened to a Nazi collaborator and called "worse than a murderer" by the couple.

They confiscated her identity card and phone and stopped paying her in a deliberate campaign to isolate her and force her to confess, the court heard.

In her final days, Ms Lionnet was hit with an electrical cable and beaten so badly she had five fractured ribs and a cracked breast bone.

She appeared broken and emaciated in a videoed confession hours before she was killed in the bath.

Her body, which the pair burned in the garden of their home in Wimbledon, south-west London, was discovered on September 20 2017 after neighbours complained about the smoke.

When asked by firefighters, Medouni claimed the au pair's body was the remains of a sheep bought from a local market.

Kouider went on to try to frame Mr Walton for the au pair's disappearance to exact "revenge" on the former boyband member.

Prosecuting lawyers told the jury Kouider was "vindictive, overbearing and controlling", while Medouni was "timid, uncomplaining and especially vulnerable to manipulation and threats".

The couple were found guilty of murder, having admitted perverting the course of justice in relation to the disposal of Ms Lionnet's body.

Jailing them for life, Judge Nicholas Hilliard QC said: "It is plain from all the evidence that Sophie was a kind, gentle and good-natured girl."

He said there was no excuse for the "horrible cruelty" and "humiliation" the defendants exacted on Ms Lionnet during taped interrogations before her death.

Orlando Pownall QC, representing former banker Medouni at the Court of Appeal, argued his conviction was "unsafe" because of a note sent to the trial judge by jurors during their deliberations which indicated they were unsure about his "intent".

He also argued his minimum term was too long, as did Kouider's barrister.

But their appeal bids were rejected by Lady Justice Hallett, sitting with Mrs Justice McGowan and Sir John Royce.

The judge said reasons for the court's decision will be given at a later date.