A mother smothered her disabled twin sons with a nappy so they would not smell her, before killing their older sister and trying to take her own life, a court has heard.
Tania Clarence (43) has admitted responsibility for the deaths of Olivia (4) and three-year-old Ben and Max at the family home in New Malden, south west London, over the Easter holidays.
She appeared at the Old Bailey, where the prosecution outlined the heart-breaking details of the case. However after breaking down and weeping uncontrollably, she was excused by the judge, Mr Justice Sweeney, and allowed to leave the dock.
Her husband, investment banker Gary, and other family members stayed behind in court. Zoe Johnson QC told the court how all three of the children had suffered from the condition SMA type 2, which is a life-limiting condition.
She explained that had they known about the condition before the twins were born prematurely on a family holiday to Portugal, they would have agreed to abort the pregnancy.
Outlining the events leading up to their deaths, she said Clarence's husband had taken their eight-year-old daughter on a holiday to their native South Africa on Friday April 18, leaving the defendant alone with her other children.
She said Clarence had given the family's nanny, known as Jade, the day off. Ms Johnson said: "We suggest that the defendant took this opportunity to end the lives of her three disabled children, although it was right to say her settled intention was only formulated on the Monday."
Ms Johnson went on: "She smothered the boys first whilst they were sleeping using a nappy so they would not smell her.
"She found it much harder to kill Olivia, and wrote a letter to her husband in the time between killing the boys and killing Olivia."
The deaths were discovered later that night after her family became concerned when they were unable to contact her and asked the nanny to visit the home and check up on her.
Accompanied by her friend Daniel Magagnin, a pastor, Jade let herself into the house and the two went upstairs.
Ms Johnson said: "They got to her bedroom door and she opened the door a fraction. She was holding a towel."
Mrs Clarence kept asking them to leave and leave her alone. She was whispering. "Daniel asked Mrs Clarence if she wanted him to pray for her, she told him to go and she said was a private person.
"Mrs Clarence started to say 'it's too late, it's too late, there's nothing you can do to help them'."
Jade gave Mrs Clarence a hug. Mrs Clarence lay down and pulled the duvet over her. Daniel noticed blood on her wrist and called 999.
"He opened the twins' door and discovered the dead bodies of the twins.
"It was such a grotesque sight Mr Magagnin could not bring himself to look for Olivia as he was instructed to do by the emergency operator."
The court heard how Mrs Clarence had written a letter to the nanny that read: "I'm so sorry I had to do this but I could not carry on. I also could not leave the children with Gary. It would have been too much for him.
"You have been such an amazing person in our lives over the last few years. Without you I most likely would have done this a lot sooner." Last month the Crown Prosecution Service accepted Mr Justice Sweeney is expected to hand her a hospital order on a later date. (© Daily Telegraph, London)