Now my son is five the terrible-twos are far behind us, but he is still capable of executing a very public paddy now and again. The full ferocity of his anger still takes me by surprise, and I have to admit to finding this sudden rush of emotion difficult to deal with.

In some respects I am jealous of his ability to be so honest about his feelings (wouldn't it be lovely if, just occasionally, we adults could scream and shout and let it all out?) but as parents we have to teach our children it is not acceptable to behave this way.

The cause of this latest outburst? Boxer shorts!

On Thursday, the school phoned to say Samuel had been head-butted (accidentally) in the face by another child. He was fine, but had had a very severe nosebleed and his clothes were covered in blood. The next day I took him to school in an emergency pair of trousers which did not have an adjustable waist. Unfortunately the trousers kept falling down and he was flashing the top of his boxer shorts. He did not seem at all bothered about this until we got to the school gates, when he suddenly decided he needed a belt.

"I am sorry, Samuel, we haven't got time to go home and get one now," I said.

But as his lip began to drop, I assured him I would deliver one to the school at break time. Unfortunately this was not good enough.

"Everyone is going to laugh at me," he said.

"Of course they're not. No one will see because your shirt covers the top of your trousers," I reasoned. "And, remember all the big boys flash the top of their boxers now – it is very cool." (As if a five-year-old cares about such things, but I was desperate!)

Suddenly all hell breaks loose.

"You're an idiot mummy!" he shouts. "I am not going to school today."

"Well you have to Samuel," I say. "So stop being so silly."

"I AM NOT BEING SILLY."

"Stop it. Everyone is looking at you and you are upsetting your friends."

At this point all his peers are lining up ready to go into the classroom, watching wide-eyed as my son starts crying uncontrollably. Then to my dismay what started as a temper tantrum escalates into something much more serious.

"I want to stay with you, mummy, I don't want to go to school today," he sobs.

A kindly teacher comes to my rescue and tries to prise my little boy off my legs – she eventually manages this leading him screaming "mummy" into the classroom.

"We'll ring you and let you know how he is doing," she says helpfully.

Sure enough 20 minutes later she calls to say he is absolutely fine – the crisis is over.

But I spend the whole day reeling, shocked by how such a minor problem could have caused such a reaction. I dare not think what would have happened if the only thing clean in his cupboard that morning had been his Spider-man costume.