For all the relentless murdering in London in recent times, you could always tell yourself that things here had not reached the stage of Miami in 1980, when homicides were committed in such quantity and with such hour-by-hour regularity that local mortuaries had to hire a refrigeration truck from Burger King to handle the overspill.

But then, a few days ago, came news of a crime that, for sheer exaggerated and revolting ferocity, rivalled any Miami vice.

Two French graduate students were tied up in a southeast London flat, probably tortured, and stabbed more than 200 times. The scene where they lay dead, and disfigured beyond recognition, was then set on fire.

What sent a jolt through even Britain's crime-hardened capital was the 243 hacks with a knife that rained down on the heads, necks and backs of the two young men as they lay bound on the floor of their rented flat.

It was just after the final of Euro 2008 came to a climax that the residents of Sterling Gardens heard - and felt - a loud, tremulous series of noises.

It drew a good number of them into the crescent-like street, and they quickly saw the source of the bangs: flames coming through the shattered living room window of flat 12.

Several neighbours ran over to see if there was anyone trapped inside. They banged on the door, but got no response. A few of them rushed to get water to throw through the windows. Soon afterwards, the fire service arrived. Inside they discovered the bodies of Laurent Bonomo and Gabriel Ferez.

It took a while to learn their identities, the extraordinary viciousness of their wounds and that, six days before, a laptop had been stolen from the flat.

Bonomo, who rented the place, had emerged from the shower on the morning of June 23 to find an intruder hurriedly leaving with his computer. The thief had forced open a living room window. Police later arrived and the room was dusted for fingerprints.

One resident saw two men hammering on the window of the flat just before the fire broke out. Another talked of seeing a white man running from the flat that evening. And, on Saturday, police said that both the students' mobile phones had been taken, as well as a pair of Sony PSP handheld videogame consoles.

Both victims were biochemistry students at Polytech' Clermont-Ferrand who had been selected for a three-month secondment to Imperial College, London, and for whom brilliant futures were predicted.

No weapon has been found, but there were traces of an "accelerant" used to set the fire. Forensic test results on these - and a container - are awaited. The use of an accelerant suggests some level of pre-meditation by the attacker(s), increasingly it is associated with often futile attempts to destroy DNA evidence. Significantly, there is no sign of a forced entry. To get inside flat 12 means first ringing the block's outside bell-pushes, and so giving those inside a look at any caller before they open the entrance door. Hence, the perpetrators had a key, were known to Bonomo, were sufficiently plausible-looking to be let in, or were already inside.

There have been suggestions that the pair's killing was a case of mistaken identity but the excess of the violence used hardly suggests a "hit". Police say privately that their strongest line of inquiry is that this attack was a robbery. They arrested a 21-year-old man in southeast London, and he is being questioned.

The key could be Bonomo's missing laptop. Maybe its contents gave its thief the idea that the student had money worth returning for. Police say the pair's bank cards may have been taken, and speculate that they were tortured to obtain their PIN numbers.

THE VICTIMS

LAURENT BONOMO

From: Velaux near Aix-en-Provence, had been a student union president in France and was immensely personable and popular. His cousin, Claude Bonomo, said of him: "He was a fantastic, fun-loving, exuberant guy."

Stabbed: 196 times

GABRIEL FEREZ

From: Prouzel near Amiens, was widely travelled, a compulsive reader of history, worked during his holidays at an Amiens hospital, and also attended a Mexican university last year. His father Olivier said: "Gabriel is, was, the most intelligent, affectionate, wonderful son anyone could ever want. He had such a bright future and now that has gone."

Stabbed: 47 times

- INDEPENDENT