Ordering 20-year-old Aaron Kelly to be detained for six years, followed by two years on probation, Craigavon Crown Court Judge Patrick Markey said that had he filled all the criteria for a diagnosis of pyromania "it would have been a question, I think, of discretionary life imprisonment".

The judge told him: "Clearly you are someone who, if not fully obsessed by fire, has a very unhealthy interest in it".

Earlier, prosecuting lawyer David McDowell said Kelly was caught in the ground of Largymore Primary School watching a fire he and a teenage girl had set and that, when he was searched, police found Sunny Jim firelighters and a cigarette lighter.

He said the teenage girl, 18- year-old Amanda Stewart, from Whitechapel Street in Nottingham, was placed on probation for two years earlier this month after she admitted to setting the fire "at this defendant's behest ".

The lawyer revealed that, so far, it had cost £150,000 to demolish and repair the school's roof and a further £30,000 damage had been caused to equipment, but "there's still no figure for the rebuild costs".

During a search of Kelly's Mercer Street home in Lisburn, police uncovered more firelighters as well as tins of white spirit and lighter fluid.

When questioned by police, said Mr McDowell, Kelly admitted to setting around 13 other fires between March and April last year including one at the Lisburn home of a woman in her 70s, one to a digger belonging to a quarry company on the Hillhall Road, to a garage and cars, and others involving derelict buildings and low-value cars.

In relation to the fire at the elderly woman's house, Mr McDowell said she had been in her bedroom as it "suddenly lit up" when Kelly pushed a wheelie bin up to a rear window beside the coal bunker and set it ablaze. She managed to escape unscathed.

In all, Kelly pleaded guilty to five charges of arson.

Defence lawyer Barry Gibson said Kelly was not a "typical, pathological fire setter" but had been examined by two psychiatrists who had both opined that some, but not all, of the criteria for a diagnosis of pyromania had been fulfilled, commenting that those were "the thorny issues I have to deal with".

Describing Kelly's offences as "worrying behaviour," Judge Markey told him his offences were "sufficiently serious to call for quite a severe sentence".