The mother of two sisters who died after an arson attack on their Tooting home relived the nightmare as she gave evidence at the Old Bailey on Tuesday.

Earlier the court heard how a jilted 14-year-old torched the house after spliting-up with the youngest daughter, Maleha Masud, 15, just over a day before.

The family-of-five were asleep upstairs when petrol was poured through the letterbox at 4.30am on June 21 last year.

Maleha died four days after the arson attack from burns and smoke inhalation, while Nabiha - a South Thames College student who was 21 and to be married four months later - died a month after her sister from organ failure.

Their brother Junaid, 18, spent 45 days in intensive care following the attack, while eldest brother Zain, 24, and the family’s mother Rubina, 55, both escaped by jumping out of a bedroom window.

A police statement by Rubina Masud, a widow, was read in court. It said: “I was woken by a woosh . . . I was half asleep. I then heard Zain [her son] say fire. The heat was intense, I went to Zain’s room . . the window was open but I couldn’t see Zain.”

After jumping, she said: “I looked around for my other children and couldn’t see them. I assumed Nabiha followed directly behind me but she was nowhere to be seen.”

Prosecuting, Jonathan Laidlaw QC told the court the relationship between the boy and Maleha was the main reason for the murders and, the teenager rang the family home and threatened to tell Mrs Masud of the relationship.

The boy used the internet to search “how to burn someone's house” hours before the attack on the Tooting home, the court was told, and saved a photo of the burnt out house after the arson as has computer screensaver.

He said: “There never could be a good or sensible explanation for the terrible things that he and his co-defendants did.”

The boy split with Maleha on Friday, June 19 about 7.30pm and was helped with the arson attack by two other men, who drove to London from the Midlands to help him “get revenge”, Mr Laidlaw said.

The boy, who is from Croydon but cannot be named, and two men, Rasal Khan, 19, from Leicester, and Shihabuddin Choudhury, 21, of Nottingham, deny two counts of murder and three counts of attempted murder.

When arrested by police after Maleha's death the boy said, "I can't believe she died", Mr Laidlaw said.

The case continues.