The train was very, very busy with half-term trippers who'd been to see the London Eye or Madame Tussauds and on to McDonalds.

They were now heading home, at peak time, laden with attraction gift shop bags and vast quantities of children.

As I made my way down the platform, looking through the windows of the carriage for a place to sit, I spotted a woman with a child beside her and what looked like two empty seats opposite.

Only when I got there, the two empty seats were actually occupied by another child, who was lying prostrate across them both.

"Ahem," I coughed and started taking off my coat, hoping that either the child would sit up and move or the mother would tell him too. But neither took any notice.

"Excuse me," I said. "Can I sit there please?"

The prostrate child momentarily reared his head and said "NO" before burying his face in the seat again. I looked at the mother for assistance but she merely shrugged her shoulders and smiled indulgently at the prostrate child.

"Is he all right?" I asked the mother. "Only it's a very busy train and there's nowhere to sit."

"I'm dead," said the boy, raising his head only to bury it again.

"Well perhaps you could be dead sitting up?" I suggested, but the boy was having none of it.

"You can't sit up if you're dead. You have to lie down," he explained and I didn't think it appropriate to go into details of how some people had heart attacks sitting up in chairs and remained sitting so that even people sitting in other chairs near them didn't know they were dead.

"Well, I'm dead on my feet," I said, looking at the mother.

"I'm sorry," she said, at last. "He has just developed an interest in death and children should be allowed to role play death to help them come to terms with the concept."

"Perhaps you should cremate him too then," said a man, watching on the other side of the aisle.

"What's cremate?" said the boy, suddenly interested in some, as yet undiscovered by him, aspect of death.

"Sit up and I'll tell you," I promised, ignoring the warning looks his mother was giving me.

The boy immediately sat up and patted the seat next to him. "How do you cremate someone then?" he asked, looking up at me with a face so full of excitement that I couldn't quite bring myself to go into details.

"Well," I hedged. "It's a way they have of tidying the body away when someone has died so they can make room for new people."

"Oh, I already know about that," said the boy, obviously wishing he'd not given up his resting place for such a useless piece of information.

"It's when they dig a big hole in the ground and put you in, then put lots of mud on top and all the worms come and eat you," he said.

I obviously needn't have worried about upsetting him with details of cremation.

"It's not exactly the same as that," I told him. "It's another way of tidying up the body."

"I know," said the boy. "I can still be dead, with you sitting there. But I can be one of the dead people in a pot . . . "

"Thank you," I said, taking out a book.

"I know where you go when you're dead," said the boy, ignoring my attempts to ignore him. "You go to Devon . . ."