Standing in her see-through floral dress, Samantha Joseph sealed the fate of Shakilus Townsend as she turned from him to send a brief text message.

Captured in a series of grainy closed-circuit television images, the 15-year-old girl looked calm and composed as she talked to Shakilus, her boyfriend of just a month, while they travelled on a bus to Thornton Heath, South London.

She had reassured him that he was only going to meet a member of her family. But rather than meeting her cousin, he was lured into the clutches of a hooded gang, cornered in a cul-de-sac beaten and stabbed to death.

As the blows from knife and baseball bat rained down on the 16-year-old, Joseph was seen laughing at their brutal handiwork. Yesterday, as she was convicted of murder, the teenager, now 16, remained stony-faced in court.

Detectives who interviewed her for several hours over three days recall her “cold and calculating” demeanour. She told the arresting officer that she could not be involved in the crime because Shakilus had been her boyfriend.

Joseph, who had no previous convictions, was brought up by her hard-working mother, Sheila, the head chef at a pub in Brockley. She lived with her mother in a flat above a bookmaker’s on the busy Brockley Road in southeast London.

The girl who showed a flair for art changed in her teens, being excluded from Norbury Manor Girls High School for fighting and was attending an education centre when arrested.

Joseph had come to Britain with her mother as a child while her father and elder brother remained in Trinidad.

“When Sam was young she was very quiet,” said one friend. “You never saw her without her mum, they were so close. But a couple of years ago she started coming out on the streets. She was very pretty and had lots of boys after her. She used to involve them in the trouble.”

One such boy was Danny McLean, a leading member of the Shine My Nine gang which had terrorised the streets of South London. She became besotted with him. Her friends worried after she complained that he often beat her. It may never be known whether this made her obey McLean’s order to deliver to him Shakilus, the boy whom he had discovered she was seeing behind his back.

Detective Inspector Barney Ratcliffe, said she had shown no remorse over the killing: “She has been very cold and callous about the incident, with no signs of emotion,” he said.

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