A French nanny whose charred remains were found in a garden was held captive and badly beaten before her death, a court has heard.

The body of Sophie Lionnet, 21, was discovered at a house in Southfields, south London, on 20 September.

Her former employers Sabrina Kouider, 34, and her partner Ouissem Medouni, 40, are on trial for Ms Lionnet’s murder at the Old Bailey.

The couple have admitted they tried to dispose of her body, but deny murder.

Prosecutor Richard Horwell QC said: “Sophie was trapped in a domestic nightmare.”

He told jurors Ms Lionnet’s body showed signs of “significant violence” including “fractures to her sternum, to four of her ribs and to her jawbone”.

The court heard Ms Lionnet lived a “bizarre and oppressive” life under French nationals Ms Kouider and Mr Medoun.

Mr Horwell said Ms Kouider accused the nanny of being “in league” with her former partner Mark Walton, who is an original Boyzone band member.

Ms Kouider had “a fixation” with Mr Walton and said he controlled her through “black magic”, the jury were told.

The court heard Ms Lionnet had gone to live with the couple shortly after her 20th birthday.

“Sophie was not only young, but also, we suggest, naive and particularly vulnerable and this made her an easy target for abuse and exploitation,” Mr Horwell said.

The court heard Ms Kouider made a series of accusations against Ms Lionnet including that she’d conspired to “sexually abuse the entire family”.

Mr Horwell said Ms Lionnet “complained that she was being beaten and that she was not allowed to return to her home in France”.

Ms Lionnet’s body was found after neighbours raised concerns about a fire in the couple’s back garden.

Mr Horwell said: “The defendants burned her body in the garden of their home in the hope that no-one would ever discover her remains.

“Their plan was to dispose of Sophie’s body and to explain her disappearance by inventing a story that she had left their employment under something of a cloud and returned to France.”

Following her death, more than eight hours of “harrowing” recordings were recovered from the defendants’ mobile phones of Ms Lionnet being interrogated, the court heard.

Mr Horwell said they depicted “a young emaciated, frightened and helpless woman”.

The trial continues.