It was parents’ evening. I approached a parent I knew vaguely - Mr Joseph - and welcomed him. In return he unleashed a torrent of abuse. He seized his daughter, Kelly, and shook her. She burst into tears. For a moment I had no idea what was making him so angry.

I needed to move him from the public arena, so I invited them to my office. He came, but stopped to pour abuse into my face. He threatened to tear my head off, to torch the school. The language was foul.

I got them into my office, only to realise he was between me and the door. I sat behind my desk, feeling that it offered me some protection. But it was obvious I could not leave.

I asked him to outline his complaint, writing down what he said. I hoped this would calm the situation. It didn’t.

Kelly had been sent home to put on her uniform. A colleague had failed to check there was anyone at home. Kelly had sat outside all morning until her mother got back.

We were in the wrong and I apologised. It made no difference. Mr Joseph accused me of playing “mind games”. It became apparent that he had been in prison and had come up against people far more skilled than myself who had tried to manage his behaviour.

Everything I said was seen as an attempt to trick him. “I know what you are doing. It won’t work. You can’t fool me.”

I continued to placate him but he continued to threaten and swear. He wanted a written apology. He wanted a response within 48 hours. He wanted to see the person who had sent Kelly home. At my refusal to comply with that, his threats became ever more exotic.

Was it all bluster? I didn’t think so. Twice, I thought he was about to attack me. He could have made worm’s meat of me. He knew it; so did I.

The word had spread. I could see through my open door that help had started to gather, including the caretaker and the cleaners. It was good to know they were there.

Mr Joseph was now shouting that Kelly could have been raped and it would have been my fault. All the while Kelly sat in the corner, crying. She was obviously frightened of him. So what was the true nature of their relationship? He was dangerous and unstable. There was something hidden here, something nasty. Soon he would leave my office. But Kelly would take him home.

He left as he had arrived. I took him to the door of the school, where he turned and screamed in my face. He swore loudly at Kelly and dragged her off.

I wasn’t frightened at the time, but afterwards I was shaking. Nothing in my training or experience had prepared me for this. How could it?

The next day I wrote him a letter. I gave him what he wanted because it is what I would have done anyway. Whatever I did would now happen in the shadow of his behaviour. If he felt he had won, then so be it. I apologised again for our mistake and told him of the steps I had taken. I also condemned his behaviour and said I had instructed staff that they should not meet with him. I informed the LEA and spoke to the police.

Yes, I got Mr Joseph off premises and he didn’t hit anyone. But what Geoff Brookes did not spell out was the impact this can have on the teacher. No strategy can prepare you for the unhinged. And no matter who you are, it isn’t nice.

The writer is a deputy head in the south of England