'WE'RE going to a town called Paris," said Jonah's mum as we settled ourselves in our Eurostar seats. "Paris is in a different country. Do you know what country it's in?" "Homebase!" said Jonah, without a moment's hesitation.

There are times when it's just not possible to understand what goes on in a child's head.

We were travelling to Paris for my birthday, all of us, me, my husband, our son and daughter, their respective partners; and Jonah.

It wasn't just for my birthday. It's a complicated story, but basically my elderly, much-loved godmother died last year, leaving the Paris flat in which she'd lived for the past 60 years for us to sort out. I wanted the family to see if there was anything they'd like to keep from it, before we work out how to dispose of what's left.

Travel agents offer a lot of cheap holidays in Paris at this time of year, because no one wants to go for romantic weekend breaks in January. You can see why - when we left home, County Durham was basking in sunshine and record temperatures. The further south we went, the lower the temperature fell and by the time we got to Paris, it was a good ten degrees colder than when we started.

The idea of wandering along the banks of the Seine or along leafy boulevards seemed plain ridiculous. There were no leaves on the trees and even the river boats weren't running. But the Eiffel Tower was there and Jonah was enchanted. "Would you like to go up it?" we asked, as he gazed up at its massive girders. He nodded, enthusiastically.

We joined the queue - shorter than usual, but still a queue. As we stood shivering among the other idiots waiting for the lift, thin flakes of snow drifted in the icy air. It was even colder once we got up to the second floor. We were glad they weren't allowing anyone up to the very top. There was a fine view, but no-one wanted to linger too long looking at it. Jonah was not impressed.

But he loved the look of the tower from down below, especially after dark when it shimmers with silver lights, like a giant Bonfire Night sparkler. So if nothing else, Paris to Jonah means the Eiffel Tower. Now he's seen it, he can recognise it immediately and takes great delight in pointing it out wherever he sees its picture, in a guide book, on a shopping bag or a teatowel.

Looking for something to do indoors, his parents took him to the Louvre - they wanted to see it anyway and thought a little bit of culture would do him no harm. They did walk past the Mona Lisa, but Jonah wasn't at all interested in some old painting of a lady. What he saw everywhere he looked were lots of pictures of Baby Jesus.

But the attraction Jonah loved best wasn't one that features on the usual tourist trail or in any guide book. He got very excited by the rockets - you know, the rockets that are parked in the Paris streets.

To you and me, they look for all the world like recycling bins - solid green circular ones, a bit different from the British type, but unmistakably recognisable as such all the same.

But not to Jonah. He knew better. He spotted the first one just outside our hotel. "A rocket!" he cried. "I want to get in it!"

When his Mum said no, he couldn't, he came out with his current favourite word: "Why?"

"Because there are aliens inside," said his mother, thinking quickly. She'd started something. We went into a cafe across the road. Jonah stationed himself by the window, so he could keep an eye on the rocket. He was convinced it was about to take off and didn't want to miss the moment of departure.

But it was still there when we left the cafe; still there the following morning. What's more, the next time we went into a cafe, there was another identical rocket parked outside. Clearly the aliens landed in Paris just for the cafes.

That set Jonah speculating as to what these visitors from outer space would choose to eat. "Aliens don't like cheese," he declared. "They only like jam." He'd obviously got to know them pretty well.

At the end of our short holiday, I do have one slight worry. When Jonah next visits Homebase with his parents, is he going to be very disappointed not to see the Eiffel Tower again in all its sparkling glory - or those jam-eating, cafe-seeking aliens parking their squat green rocket?