Clive Bent, described by neighbours as 'the nicest man you could wish to meet', had tried the police, his local MP, raised a petition and even written to the Prime Minister to try to get help over the problems caused by his upstairs neighbours.
The flat in north London, rented by Georgina Owusu, often had as many as eight people living there and apart from the noise, Bent and his wife were woken at all hours of the night by people calling for drugs, John Nutting, for the prosecution, said.
In May this year Bent, 60, warned Mrs Owusu, a mother of four, what he was going to do and gave her half an hour to clear her children and her belongings from the maisonette.
But she left her two small sons aged three and six to find their own way out and they were trapped in the dense smoke when Bent sprinkled petrol over the stairs and set them on fire. The six-year-old jumped to safety from a first- floor window, but three-year-old Prince Owusu died in his bedroom.
Bent later told police: 'They are selling drugs, they are partying. I phoned Stoke Newington police station - they said phone the drugs people. I phoned Scotland Yard - they said they could do nothing.
'Mrs Owusu bangs on the floor. This morning I could not take any more. I had had enough. I could take no more.'
Bent, of West Bank in Stamford Hill, denied murder but admitted manslaughter on the grounds of diminished responsibility. He was sent to a secure hospital without limit of time after Judge Henry Pownall heard he was suffering from mental illness.