A man was arrested last night on suspicion of the murders of two French students.

Daniel Sonnex, 23, who lives less than half a mile from the flat where Laurent Bonomo and Gabriel Ferez were tortured to death, was arrested in Peckham, southeast London, half an hour after police made an appeal to trace him. His brother, Bernard, 35, was arrested on Wednesday.

A police source said that Daniel Sonnex, also called Dano, was well known to police and had been previously detained in relation to incidents of serious violence. His parents, Kathleen and Bernard, both 55, live in a terrace house in New Cross. His brother and a 25-year-old woman were arrested at their home in Streatham, South London, and were still being interviewed by police last night in connection with the inquiry.

A third man, Nigel Farmer, 33, appeared before Greenwich magistrates charged with the two murders. He was also accused of arson and attempting to pervert the course of justice by starting a fire, allegedly to destroy evidence. He spoke only to confirm his name and that he had no fixed address. He was remanded in custody to appear at the Old Bailey on October 16.

Mr Farmer, who is unemployed, was arrested on Monday after walking into a police station with burns to his hands and face. The badly burnt bodies of Mr Bonomo and Mr Ferez, both aged 23, were found after an explosion at a rented bedsit in Sterling Gardens on June 29. Mr Bonomo had been stabbed nearly 200 times while Mr Ferez had suffered nearly 50 knife wounds in what has become known as the “Tarantino murders”.

Investigators found that the two men had been bound, gagged and tortured before petrol or a similar inflammable liquid was splashed on and around their bodies. Police said that a strong smell of accelerant remained at the property hours after the blaze had been put out by firefighters.

They said that scientific work at the ground-floor flat in Sterling Gardens could last several more weeks.

Six days before the killings, Mr Bonomo disturbed an intruder stealing a laptop computer. Experts found no evidence of forced entry after the murders, suggesting that keys might also have been stolen. Two Sony handheld games consoles were also taken and credit cards are believed to be missing.

Neighbours at the house in New Cross where the Sonnex family are thought to have lived for more than 20 years said that armed police arrived at about 8pm on Wednesday and battered the front door down.

Patrick Norton, 79, said: “On Wednesday night I came out at about 9.20pm and I couldn’t get out because a policeman stopped me. There was a policeman with a gun pointed straight at the nearby house. The police have been here ever since.”

Louise Sonnex, sister of Bernard and Daniel, declined to speak at her home, also in the New Cross area. Her boyfriend said: “She’s very upset. She got a call yesterday to say that police had gone to her parents’ home and that they had entered it. They were not there at the time. She also got a phone call to say that Bernard had been arrested.”

Mr Bonomo and Mr Ferez had come to London for three months to work on a DNA project in the life sciences department at Imperial College. French newspapers said that the murders highlighted how dangerous London has become. Police arrested 1,200 people and seized more than 500 knives in a six-week crackdown.

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