The fiancée of one of two French students found brutally murdered in a bedsit in southeast London wrote today of her grief and her wish for his death to be avenged.

Mary Bertez, a student at Valenciennes University in northern France, described her anguish on Laurent Bonomo’s page on Facebook, the social networking website.

The young woman left a message for her 23-year-old fiancé this afternoon, two days after she learnt of his killing alongside Gabriel Ferez, also 23, on Sunday night. The pair were bound and gagged before being stabbed a total of 250 times. Their bodies were then burnt as the flat in New Cross was set on fire.

“My love, unfortunately I was not there that night, we who are always together,” she wrote. “I do not stop thinking about you every second . . . I have lived ten months of happiness that I never lived until then. Today you left. I will try to be as perfect as you always wanted me to be.

“I will give all necessary information for the investigation, my dear, so that you can be avenged. I love my ‘doudou’ from the bottom of my heart.”

Detectives say that Mr Bonomo was stabbed 196 times, 100 times in his back when he was already dead. Mr Ferez was stabbed 47 times.

Detective Chief Inspector Mick Duthie of Scotland Yard's Homicide and Serious Crime Command, who is leading the murder investigation, said: ""I have never seen injuries inflicted to bodies like this before."

The two were on a sought after three-month research placement at Imperial College London, where they had impressed colleagues with their maturity.

The college said that Mr Bonomo was studying a parasite that can spread from cats to human foetuses. Mr Ferez’s research was into bacteria that create ethanol for use as fuel.

Speaking at his press conference, Mr Duthie said that a fire accelerant had been sprayed around the ground-floor flat in Sterling Gardens before it was set alight. A white male was seen running away from the area — although a neighbour told reporters today that two men had been seen banging on the outside of the flat's windows shortly before a loud explosion.

Mr Duthie said that members of the dead men's families arrived in London yesterday and had the "gruesome" task today of identifying their sons formally.

Mr Bonomo was from Aix-en-Provence and Mr Ferez from near Amiens but most of those who paid tribute to Mr Bonomo on his Facebook page today knew him from the Polytech, an autonomous institute at the Clermont-Ferrand university where both men studied bio-engineering.

Caroline Durand — a fellow student in Clermont-Ferrand — attempted to contact him on Monday evening. She hoped that a group e-mail she had read discussing his death was a “damned stupidity”. She wrote: “Reassure me!”

Laurent Steven, another friend, also begged to hear from him. “Come out of your hole and come and tell us that is was a bad joke,” he wrote.

The truth was confirmed by Aurelien Jeandot, who said that Mr Bonomo’s mother and fiancée had called him on Sunday night because they were worried. Mrs Bonomo called again on Monday afternoon to confirm the worst.

Ms Durand said that Mr Bonomo's and Mr Ferez’s deaths were announced to their fellow students on Monday. “All the school is distressed and the messages of support and condolences flow. I do not know you all but I wanted to wish all of you who knew Lolo courage. All my condolences go to his family, and my thoughts are with Mary whom I have not had a chance to meet but about whom Laurent told me a lot.”

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