A jealous girlfriend known as “princess” was today jailed for life for murdering a young Chinese graduate whose headless body was found floating in a marina.

Xing Xing Xie had her head cut off while she was still alive in a killing whose brutality stunned detectives.

Noor Mohd-Yusoff had sent the 23-year-old a text message threatening to kill her just days earlier, the Old Bailey heard.

She was possessive of her boyfriend Trach Lon Gian and told friends they were husband and wife, jurors were told.

Mohd-Yusoff, a 22-year-old Malaysian prostitute, collapsed sobbing in the dock today as she and Belfast-born Gian, 27 and of Vietnamese origin, were both found guilty of murder.

Gian, who was also found guilty of perverting the course of justice by disposing of the body and had a previous conviction for wounding, was told he must serve at least 22 years. His girlfriend was given a minimum of 15 years.

The court heard that in April last year, she returned to their home in New Cross, south east London, to find Xing Xing there following a 36-hour pornography and cocaine-fuelled party.

Two days later her headless and handless corpse was discovered floating in a laundry bag by a horrified couple who lived in a house boat in the South Dock Marina in Bermondsey, south London, prompting a massive police murder hunt.

Seven weeks later the decapitated head was found, wrapped in black plastic bin liners in an adjacent dock.

Tests showed Xing Xing had her head cut off while she was still alive and was intoxicated with a potentially lethal level of cocaine.

A post mortem examination showed 37 separate knife wounds.

Traces of her blood were found at Gian and Mohd-Yusoff’s home in Knoyle Street, New Cross. An eight-inch knife and cleaver were missing from the kitchen.

The couple had fled to the Birmingham area where they were arrested in July.

Mohd-Yusoff was crying uncontrollably and told an officer: “I slapped her, I beat her up. By mistake she died.” But later she changed her story and denied any involvement in the killing.

The court heard that on March 31, just over two weeks before Xing Xing died, Mohd-Yusoff had been treated by an ambulance crew after hitting herself over the head with a small Buddha statue.

She said she had “just found out that her husband was having an affair”.

Brian Altman QC, prosecuting, said Mohd-Yusoff’s jealousy was “one possible motive” behind the murder.

He said: “She was known to be jealous of his relationships with and closeness to other women.

“She appeared to be possessive of him and referred to him as her husband and to herself as his wife.”

A third man, Chanh Ngo, from Vietnam, is also believed to have participated in the murder but has since fled the country.

Jailing the murderous couple, Judge Giles Forrester said: “The attack was vicious and cruel. Not only was she stabbed twice in the neck, she was indeed decapitated whilst alive.

“She was a defenceless and vulnerable woman. What actual part each of you played I cannot say, but each of you did play a part in the foul deeds of that day.”

Detective Chief Inspector Carl Mehta, who led the investigation, said: “The brutality and savagery shown by Xing Xing’s killers is something I have not come across before and beggars belief.

“Xing Xing came from the Sichuan province of China, from a well respected academic family background.

“She came to the UK in 2002 to study and was a successful student at Liverpool University before coming to London to work.

“Her family have had to suffer the loss of a daughter many thousands of miles from home, in an unfamiliar city, and in the most harrowing and tragic circumstances.

“My sympathies are with them today. Nothing will bring back their daughter but I hope they are able to draw some comfort from the fact that her killers have now been brought to justice.”