A “DANGEROUS” drug addict – who sparked a blaze at a block of flats while snorting butane gas – is to be released from prison later this year after top judges quashed his potentially lifelong jail term.

Heroin addict John Davidson Scott collected gas cylinders and kept them under his bed so he could get high from inhaling the fumes.

But, despite being warned about the containers by his landlord, 41-year-old Scott lit a cigarette while sniffing the gas in November 2009, causing a fire at his flat in Willow Way, Hatfield.

After he was convicted of arson last year, a judge at Luton Crown Court ruled he was a danger to others, and handed him an indeterminate prison sentence for public protection.

The punishment, almost identical to a life sentence, meant Scott would only be freed if he could convince the parole board that he was no longer a threat to society.

But three senior judges at London’s Court of Appeal last Tuesday overturned that decision and imposed an extended sentence – which could see Scott back on the streets in November this year.

Judge Peter Collier QC told the court Scott had been living in a house of multiple occupancy in Hatfield, was addicted to heroin and snorted butane gas from cylinders which he bought “in bulk”.

The judge said Scott was warned about the canisters by his landlord, but weeks later smoked a cigarette while inhaling the gas. He later told police his cigarette lighter caught fire and he threw it away before noticing a fire had started.

He ran to warn his neighbour, and nobody was hurt in the blaze, which gutted the flat Scott was living in and damaged surrounding properties.

Scott said he had not been reckless and the fire was an accident, but the jury found him guilty of arson.

The judge said Scott had been convicted of another offence involving a fire in Scotland some years before, and a medical report found he lived a “chaotic lifestyle”.

But lawyers for Scott claimed the judge over-estimated how dangerous he was and his open-ended sentence was therefore “manifestly excessive”.

Judge Collier, sitting with Lord Justice Pitchford and Mr Justice King, ordered the indefinite term be quashed and replaced with an extended sentence or four years in jail and four years on licence in the community.

He said: “The question for us is whether an extended sentence can sufficiently manage the risk to the public posed by the appellant. We have come to the conclusion that it can.

“It seems to us that the terms of licence to which he would be subject after his release would be such as could prohibit the possession of butane gas cylinders and enforce attendance of a number of courses, sooner than he would be able to take them in prison.”

Scott will be entitled to automatic release after serving half of his custodial term. His barrister said this meant he should be freed in November this year.