He had turned up in school to make a complaint about the school buses. His grandson had not been allowed to get on the bus so he had to bring him to school in the car. This was clearly not on his agenda for the day.

I found the old man in the school office, shouting in an abusive fashion at the staff. It was particularly vile. I intervened and invited him to my office in the hope that I could calm him down. As we went along the corridor, he continued to swear and, once in my office, he exploded again, shouting and waving his arms. He refused to sit down.

I started off calmly. I asked him to explain his problem and said that I would do what I could. It was when he started to threaten me, rather pathetically, that something inside me snapped.

It was first thing in the morning. I had not gone to school that day with the intention of being abused. So I shouted back at him, about his manner and his behaviour. He had no right to shout at the office staff. They had nothing to do with the buses. I told him that he had to leave the premises.

He gasped, shocked, and leant back against the wall. “Don’t shout at me. I’m a geriatric. I’ve got asthma.”

It was only afterwards that I realised how ridiculous his comments were.

At the time I told him neither the buses nor the asthma were my problems. I escorted him to the front door and told him to leave. He clutched at the handrail and walked back to his car, complaining breathlessly about his treatment.

Of course I felt guilty. He was an old man operating outside his environment, blah blah, and I have a duty towards the community, blah blah, and to preserve the image of the school, blah blah. But he had no right to do what he did. We not a therapy centre for anyone with a grudge.

Usually we listen. We have to. We never know who we are dealing with or what state they are in. By reacting as I did I could have made matters so much worse. But teachers have rights too and, on this occasion, I followed my instincts.

Later I saw the old man’s grandson. That morning he had forgotten his bus pass so the driver would not let him on.

“Don’t worry about my Bampa,” he said. “He’s a nutter.”

Ian Roe is a secondary teacher in north Wales