The sister of Kristy Bamu, the 15-year-old allegedly tortured to death after being accused of witchcraft, sobbed at the Old Bailey as she recalled the days leading up to his death.

Jurors have heard that he died at the hands of his sister and her partner in “a tale of horror” on Christmas Day 2010 in their flat in Hathaway Crescent, Manor Park,

Magalie Bamu, 28 and Eric Bikubi, 27, are said to have attacked Kristy and his two sisters with pliers, knives and a hammer after accusing them of being “sorcerers,”

The boy suffered 101 injuries. His face and head were covered in cuts and some of his teeth were missing when he was found in the blood-soaked flat.

He died from a combination of his injuries and drowning in what prosecutor Brian Altman QC said had involved “unspeakable savagery and brutality”.

Bamu told an ambulance service operator her brother had drowned himself in the bathroom.

In evidence his Kelly Bamu, now 21, said she was visiting London with the 15-year-old, their two brothers and a younger sister, over Christmas 2010.

She told the court the atmosphere in the first few days had been “nice”.

But the mood began to sour when Kelly heard an incident involving her brothers, Bikubi and Magalie, going on in the flat’s kitchen.

“I didn’t see anything, but I heard some noise,’ she said.

Kelly told prosecutor Andrew Altman : “The reason was that Kristy had wetted his pants and he tried to go and hide them. That’s what triggered everything – all over a pair of pants.”

Kelly said the incident had raised Bikubi and Magalie’s suspicions that she, Kristy and their younger sister were practising kindoki – a form of “sorcery” that pervades society in their native Congo.

“Magalie and Eric said that the pants that had been weed on were bewitched,” she said.

“Both of them said that we had come to their place to cause harm to them.

“It was as if they were obsessed by witchcraft and then it became unbearable.”

Speaking about her sister Magalie, she added: “I’m sure she still believes, even until this day, that we are witches.”

As she recalled the beating inflicted on Kristy, she turned to the dock and gestured to her sister before shouting: “You are an idiot.”

The couple deny murder and causing actual bodily harm to Kelly and an 11-year-old.

The trial continues.