Couple 'killed naive French nanny, 21, then burnt her body in the garden of their £900,000 London home after accusing her of using black magic and stealing a diamond pendant during "brutal inquisition"'

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The charred remains of Sophie Lionnet, 21, were found in a garden in South West London

A designer murdered a young French nanny and burnt her body after accusing her of 'outlandish' crimes she had not committed, the Old Bailey heard today.

Sabrina Kouider, 35, the ex-girlfriend of Boyzone founder Mark Walton, allegedly killed 'naive and vulnerable' Sophie Lionnet, 21, after a 'brutal and oppressive inquisition' that saw her starved, mistreated and violently assaulted.

Kouider and partner Ouissem Medouni, 40, who are also French, are said to have held her prisoner at their £900,000 home in Wimbledon, South West London, in the days before her death.

The court heard 'malevolent' Kouider accused her of being 'in league' with Mr Walton and in rambling complaints said he controlled her through 'black magic'. 

Kouider also allegedly accused the nanny of stealing a diamond pendant and plotting against her.

Richard Horwell QC, prosecuting, said: 'The last days and hours of Sophie's life must have been truly wretched. She was subjected, at times, to a brutal and oppressive inquisition and to significant violence.'

Miss Lionnet died after suffering fractures to her sternum, four ribs and her jawbone. Kouider and Medouni then allegedly tried to cover up the murder by burning her body in their garden.

A court sketch of Ouissem Medouni (left) and Sabrina Kouider (right) at the Old Bailey today

Mr Horwell said: 'The plan was to dispose of Sophie's body and to explain her disappearance by inventing a story that she had left under something of a cloud and had returned to France. Another missing person, no longer their responsibility, her disappearance nothing to do with them.' 

Their plan was only foiled when a neighbour became concerned about the fire and dialled 999, jurors were told. Ms Lionnet's charred body was discovered at the house on September 20 last year.

The young victim, from Troyes, north-east France, had moved to the UK in 2016 to improve her English. Mr Horwell said: 'Sophie was trapped in a domestic nightmare.'

He added: 'Sophie was not only young, but also naive and particularly vulnerable and this made her an easy target for abuse and exploitation. Sophie had a big heart but was not worldly wise and it was easy to take advantage of her.'

Miss Lionnet's health began to deteriorate in the period leading up to her death because of her 'bizarre and oppressive' life, the court heard.

'At times she appeared scared and hungry,' said Mr Horwell. 'She complained that she was being beaten and that she was not allowed to return to her home in France.'

Kouider was allegedly seen shouting and screaming at Miss Lionnet. She accused the young Frenchwoman of stealing a diamond pendant and plotting against her, the court heard.

Mr Horwell said: 'Precisely what was in Sabrina Kouider's mind may be difficult to determine but it seems that the more outlandish the allegations the more she pursued them, despite the fact they were denied and despite the fact there was no evidence to support them.

Medouni, 40, and his partner Kouider, 35, of Wimbledon, South West London, deny murder

'Her allegations appear to have been contagious because Medouni was beguiled by Kouider and her obsessions and delusions and he began to adopt them himself.

'Eventually they confronted Sophie and wanted her to confess to conduct and crimes she had not committed. Sophie became a prisoner in the Wimbledon home and she must have been terrified.

'The defendants mistreated and intimidated Sophie in a manner that is way beyond anything that could be considered normal or rational.

'Sophie must have found this unnatural and increasingly toxic situation wholly outside her experience and ability to manage. At times she made confessions to please her oppressors and then would withdraw them.

'And so the pressure increased and so did the violence against her.'

Jurors were told Kouider had been in a relationship with Mark Walton.

Mr Horwell described Mr Walton as 'an original member of the successful Irish boy band Boyzone' who now lives in Los Angeles.

Kouider started to rent the ground floor flat in August 2013.

Mr Walton paid for the first month's rent and deposit of over £4,000 and another five or six months rent, jurors were told.

The court heard Kouider (pictured) accused her nanny of being 'in league' with Mr Walton and in rambling complaints said he controlled her through 'black magic'

She later 'got into significant rent arrears' after the payments stopped.

Kouider worked from home as a fashion designer but was 'not particularly successful' the court heard. She got to know Ms Lionnet from January 2016.

The victim had studied a vocational training course in child care and wanted to work with children. She last saw her mother at around the time of her 20th birthday.

The court heard 'inquisitive' firefighters discovered Sophie Lionnet's remains under the ash of the fire in the garden.

'Without such vigilance the two defendants might well have got away with murder - which was, of course, their aim,' said Mr Horwell.

The prosecutor told jurors that it was understandable if the case appeared 'difficult to believe at first blush'.

'How can someone be treated in such an appalling manner and not leave?' he asked. 'How can someone confess to fantastical allegations which are not true.

Kouider is the ex-girlfriend of Boyzone founder Mark Walton (pictured)

'It is likely that never before will you have encountered a combination of individuals such as these two, Sabrina Kouider and Sophie Lionnet.'

Kouider was 'vindictive, overbearing and controlling' while Sophie Lionnet was 'timid, uncomplaining and especially vulnerable to manipulation and threats.'

Mr Horwell said it was 'a unique and highly dangerous combination that led to murder and the attempted disposal of a body.' 

Kouider was 'obsessed with Mark Walton and complained that he was stalking her', according to one witness.

The prosecutor said the 'love between them ended some five or so years ago.'

'On Kouider's part, that love soon turned to anger and bitterness,' added Mr Horwell. 'You may conclude that it turned into a form of obsession.'

Miss Lionnet allegedly confessed she was being 'beaten' by Kouider to a local fish and chip shop owner.

She regularly visited the takeaway, often dressed in the same clothes, to eat chips at speed as if she was hungry, the court was told.

Miss Lionnet said she wanted to go home to France because her mother was unwell but was not allowed.

In August 2017 Kouider yelled at Miss Lionnet in a high pitched voice and called her a 'bitch', it is claimed. Kouider was also seen by a friend accusing Ms Lionnet of stealing a diamond ring, the court heard.

Catherine Devallonn (left) and Patrick Lionnet (right), the parents of Miss Lionnet, are pictured outside the Old Bailey this morning

The same witness was present when Kouider knocked Ms Lionnet to the floor during a row in the summer of 2017, it is claimed.

'Sophie was on the floor, holding her head and crying,' said Mr Horwell. 'She had obviously been assaulted.'

Kouider was in a 'total rage', the court heard. The prosecutor said Sophie was 'trapped in a nightmare and tragically there was much worse to come.'

Kouider and Medouni threatened Miss Lionnet with rape and violence as they 'interrogated' her over the six weeks before her death, the court heard.

Mr Horwell said: 'They exerted considerable and ever increasing pressure on Sophie to make confessions.

'They interrogated Sophie over some six weeks leading up to her death, sometimes calmly but more often than not aggressively - threatening her with prison, rape and violence if she did not cooperate.

'The extensive nature of these menacing interrogations is known because the defendants recorded them.'

Jurors heard there were eight-and-a-half hours of audio recordings on Kouider and Medouni's mobile phones.

There were also three video recordings made on September 18. 'They must have been made soon before Sophie was murdered,' said Mr Horwell.

'They are harrowing. They depict a young, emaciated, frightened and helpless woman anxious to say and do whatever her two tormentors wanted her to say and do but her exhausted and terrified state was such that it is obvious that she was not always certain what it is they wanted of her.'

Police also found notes written by Miss Lionnet complaining about being called a 'whore', 'bitch' and a 'slut'.

On one piece of paper she wrote: 'I wish to go home... I need a break... I miss my family, my friends - my family first and foremost.. so please, I am asking this for the last time, I want to go home. My mother told me that if you don't let me go she was going to send the French Embassy'.

The remains were discovered in a garden at a house in Wimbledon on September 20 last year

The prosecutor said the killers were able to 'control and manipulate Sophie' so that she did not simply leave the UK.

In another note she wrote: 'I would like to speak about my returning to France.

'I have not even gone back a single time, neither for a weekend, nor a week during the holidays, nor the summer holidays, nor Christmas, or New Year.

'It has been a long time. My family, my friends, my relatives, I miss them a lot, my family most of all. They miss me a lot also and don't stop demanding my return and are fed up hearing the same reply, which is 'soon''.

Miss Lionnet also sent revealing messages to her father and mother, the court heard.

On 25 June last year Miss Lionnet wrote a letter to her father Patrick about the abuse she was suffering, the court heard.

She said: 'I have to say sorry for the long wait without news. I no longer have Internet access and do not have enough credit to phone France.

'I should have written this little letter some time ago, but I have been very worried about what is happening here.

'There are a lot of tensions and I'm being accused of things that I would NEVER dare to do. In short, suddenly I feel worried.'

Miss Lionnet told her father she was coming back 'very soon' in July 2017.

She initially told her mother Catherine Devalonne, who was living in France, she was 'happy' in the UK.

But during the last six months of her life she revealed that she was 'bored' and wanted to come home, the court heard.

A court artist's sketch shows Medouni and Kouider appearing at the Old Bailey last September

As early as August 6, 2016 Miss Lionnet told her mother in a Facebook message that she had been accused by Kouider of stealing a diamond pendant.

It read: 'She says she won't let me go until the pendant has returned to its place of origin. And she would press charges against me.

'She says that she does not mind what the police would do, all she wants is that pendant. I am fed up with this place. I can't stand it anymore, I don't know what to tell her.'

In November 2016 Miss Lionnet asked her mother to send some money so she could buy a ticket home - but sadly her mother could not afford it.

Then in February 2017 Miss Lionnet told her mother that Kouider had offered to hire her as a fashion model, the court heard.

'I am willing to help because I like fashion, but on the other hand I would really want to be back home,' she said.

Miss Lionnet again asked her mother for some money to return home on 3 August 2017 and received €40, jurors were told.

Her mother replied: 'Hello Sophie, I have put the €40 in your account. Take care, see you Monday, kisses.'

Miss Lionnet did not return home and four days later the recorded interrogations began, the court heard.

Miss Lionnet's mother sent a desperate text messages including one on 4 September last year reading: 'Hello Sophie, how are you? What's happening, I'm not sleeping even with the help of tablets at the moment. 

'I hope nothing has happened to you. I miss you my daughter. I love you come home soon even if you are ill or there is something else, kisses.'

Medouni and Kouider, both of Wimbledon, South West London, both deny murder. The case is expected to last for up to five weeks. The trial continues.