Students Gabriel Ferez and Laurent Bonomo were tied up and stabbed
A man accused of murdering two French students in south London has admitted setting their bedsit alight but said it was after his children were threatened.
Nigel Farmer told the Old Bailey the brother of co-defendant Dano Sonnex threatened to harm his children if he did not carry out the arson attack.
Laurent Bonomo and Gabriel Ferez, both 23, were stabbed hundreds of times in their New Cross bedsit in June 2008.
Mr Farmer and Mr Sonnex deny murder, false imprisonment and arson.
Mr Sonnex, from Peckham, south London, admits one count of burglary, which his co-defendant denies.
Father-of-two Mr Farmer, 34, told jurors that Dano Sonnex's brother Bernie Sonnex had in the past admitted killing three other people and getting away with it.
"He said to me, 'Have you seen how much blood Dano had on him this morning?'," said Mr Farmer.
"He said, 'If you don't do what you're told, tomorrow morning that could be your kids' blood all over him."
"He was obviously scaring me quite a lot. Dano came in and he said he could cut my kids' legs off below the knees."
The conversation was alleged to have taken place in the hours following the murders.
Mr Farmer described how he had gone into the bedsit and been caught up in a fireball after sprinkling petrol around and setting fire to it with a match.
He said he was only in there for 30 or 40 seconds and had not seen the bodies of the students as the lights were off.
"I practically ran through it, sprinkling petrol," Farmer said. "I threw the jerry can back into the flat and I lit a match and I was engulfed in a fireball."
Earlier, Mr Farmer told the court he had returned to the Sonnex family home in Deptford where he was staying at the time, following a night out with his co-defendant.
He said he was dozing on the sofa when Mr Sonnex came in at about 8.30am covered in what looked like blood.
"He stood in the hallway, he was crazy-looking," Mr Farmer said.
"His trousers had red staining on them and there was staining on his jacket and jacket sleeves. He was wide-eyed and sweaty.
"I asked him what had happened and he shrugged it off and laughed."
Mr Farmer said Sonnex had also tried to burgle the home of EastEnders actress Maureen Bass, who plays Mo Harris in the BBC soap, shortly before the murders.
A friend who disturbed the intruder described how he had climbed on top of the conservatory and when confronted said he wanted "Mo's signature" before fleeing.
The court heard she called police at 0500 BST, half an hour before the killings of Mr Bonomo and Mr Ferez.
The trial continues.