Coping with the stories some of his pupils come up with is easy for Iain Petrie. Long before he heard of “the dog ate my homework”, he had encountered “the dog ate my giro”. He heard them all during his 10 years working for the Benefits Agency - from alien abductions, to witchcraft and wizards, to birds flying off with wads of cash.

“You come across some mad things. One man came in to claim a Social Fund loan because he had no money and it was nearly two weeks until his next payment,” he recalls. “When I asked him what had happened to all his money, he said that when he came out of the post office after cashing his giro, a bird had swooped down and snatched his money from his hand. I asked him what sort of bird and he said he thought it was a sparrow.”

He quotes another woman who was claiming incapacity benefit because she was suffering from stress. “She put on her form that she was hearing voices, yet in the section on jobs she put down she wanted to be an audio typist.”

Mr Petrie almost went into teaching straight after university in 1988. “I was always drawn to it,” he says. “I think it is the actor in me, looking for an audience. But I tried my damnedest to avoid it.”

He did a week of teacher training after his degree in English and a postgraduate degree in Scottish literature before giving up to become one of the most over-qualified storeroom assistants Argos has ever had. He jacked that in for a job as a museum warden at Edinburgh Castle. But the allure of the Benefits Agency was too much, and he became a fully fledged member of the civil service.

“I was put on counter duty when I joined because they reckoned working at the museum had given me expeience of dealing with the public. But nothing prepares you for counter work at the Benefits Agency,” he says. “It was the most intimidating job I have ever done.”

He dealt mainly with people claiming incapacity benefit or those who hadn’t received or had lost their giros. He was shouted at, abused, threatened with a gun and spat on. But he says his time at the agency honed his diplomatic skills and makes any threat in the classroom look much less scary. “I was also used to seeing burly policemen called to deal with some disturbance or other. They always seem to send the burly ones down to the agency offices, and it’s the same in schools.”

In 1996, Mr Petrie was promoted to a managerial position at head office in Newcastle. There he dealt with complaints and produced procedural guidance.

“It was an incredibly tedious, repetitive job. The agency is still a dinosaur and everything is paper-based. All the files of students’ work I have to organise now remind me of it. But at least I have the administrative skills to cope.”

The boredom and the need to have a face that fits finally took their toll and Iain Petrie once again felt the pull of teaching. Luckily for him, Moray House College in Edinburgh was waiving fees for English teachers the year he applied, so he left his well-paid, office-bound job and headed back to Scotland.

He graduated a little over a year ago and says he’s enjoying life at Grangemouth high school. But he never hides his past. “The kids are fascinated to know about my experiences. They ask lots of questions, especially about my time as a baker - which I did for two years after school. I’m glad to tell them. I want them to get a glimpse of what it can be like out there, to encourage them to try for better things.”