A glance at the word, indeed, even a study of the word if you're not thinking straight, will suggest that it's said something like "Parasophulus" but it isn't. Ask Thomas. Eventually, I get it right, and we're able to move onto Compsognathus, which is slightly easier.

You'll have guessed from all this that Thomas has reached that period in his life that a lot of parents and grandparents will recognise. We scientists call it The Jurassic Period; it's the time when young boys and, to a lesser extent in my personal experience, girls, become obsessed with dinosaurs.

With Thomas, it's happened over the last couple of months, I reckon. For a while he could take dinosaurs or leave 'em; he preferred cars. And, like the dinosaurs to come, he loved the names. We'd be going down the street and he'd be listing the car names, like a salesman at a garage.

Then, as the summer came on, the dinosaurs began to take centre stage. We got my lad Andrew's old baskets of toy dinosaurs out from under the spare bed and Thomas was in heaven.

We'd divide them up into meat-eaters and plant-eaters and the meat-eaters would endlessly chase the plant-eaters across the carpet, sometimes trapping them by the settee, sometimes allowing them to escape into the conservatory.

We then went to spend a few days with my mother-in-law at her caravan in Cleethorpes and she showed us a book she'd picked up for him from a charity shop.

"It'll do for him when he's older," she said. Little did we know. It's called My First Encyclopedia: Dinosaurs and over the next few days my wife and I must have read it to him 100 times.

I can tell you now, from memory, that skulls show that the male Parasaurolophus has a longer crest than the female, and that male dinosaurs may have used their crests and horns for showing off to females and that Stegosaurus weighed six or seven tonnes, so it was as heavy as an elephant, but it had a brain the size of a walnut.

Thomas loved that bit and we talked for a while about how big a brain a dinosaur would need. We concluded that if your brain was the size of a walnut there wouldn't be much room in it for things like thoughts.

When we got home from Cleethorpes, we brought the book with us; in one sense we didn't need to because he knew it off by heart.

He'd use one of the meat-eating toys to attack a plant-eating toy and instead of saying 'Grrrr!' like he might have done in the time BCSDB (that's Before Charity Shop Dinosaur Book) he would say: "I'm tearing the Brachiosaurus's flesh using the sharp spike on the end of my thumb!"

In the back garden, we built two lands: Meat-Eater Land was on a table at the bottom of the garden, near the house. Plant-Eater Land was on a table at the top of the garden in a shaded area near the big tree in the cemetery.

The Meat-Eaters made endless raids on the Plant-Eaters, sometimes having a bit of a cease-fire as Thomas had a go on the swing half-way down the garden.

Sometimes we discussed the thorny problem of extinction.

Thomas favoured the meteorite method, a meteorite coming
down to Earth and (in his interpretation, any way) flattening them all, and we'd be playing away when suddenly he'd shout "Meteorite" and we'd have to duck for cover under the table in an echo of older government policy in case of a nuclear attack.

Oddly, it always works, and if it happened, as it sometimes did, that all the dinosaurs got killed, Thomas would just say that they were alive again and, do you know what, they were.

The last couple of days, though, cars have begun to jostle for his attention again. We'll be playing at dinosaurs and then he'll say "Let's have a race" and we're both cars.

He'll ask me how many exhausts I've got and I'll say one. I'll ask him how many he's got and he'll say ten hundred twenty.

He'll ask me how big my spoiler is and I'll say small. I'll ask him how
big his is and he'll say huge. Just like the Parasaurolphus using its crest and horns for showing off, I guess. He revs up and we're off down the garden.

I prefer dinosaurs, to be honest, it's less exertion for a grandad with a brain the size of a walnut.