Yesterday morning he came into my bedroom and said in a very worried little voice:

"Mummy, I don't know what to do. I thought Luke would be here by now."

(Luke is one of his school friends.)

"Why on earth would Luke be here," I asked, still half asleep (it was 6.30am after all).

"Because he is coming to pick me up in his rocket," he said, in a voice which implied I was very stupid for not understanding.

"Oh, and why would he do that?" I asked.

"Because we want to go to heaven so I can see Tilly and give her a stroke," he said earnestly.

Those of you who are regular readers of my column will know that Tilly was our pet cat, who back in May this year was unfortunately run over by my poor husband. She was 18 and we think must have been going a bit senile, but we all miss her very much.

Two weeks ago, in a bid to fill the huge void Tilly's departure has left in our lives, we got two kittens from the Cat Protection League.

Samuel, with an honesty only a young child can express, said: "It is a good idea to get two kittens, mummy, because if daddy runs over one, we will still have one left!"

Although, the new additions to our family have made a big impression on us all, they are no Tills. Where Tilly was gentle and friendly, the kittens are skitty and playful. They attack your feet when you walk past (which has caused Samuel to walk on the furniture, rather than the floor) and claw your clothes when they jump up for a cuddle.

Of course, I know that as they get older they will calm down, but I think poor Samuel, who just wants to pick them up all the time, doesn't understand that they just want to play.

When I told him that even a space ship would not be able to take him to heaven.

He looked at me incredulously and said: "Not even if it has a turbo jet engine?"

"Um . . . no," I said.

"Can we give Tilly another stroke then?" he asked.

"How are we going to do that sweetheart, she isn't here any more, is she?"

"We can dig her up and give her a cuddle. I think she needs one from us, mummy, she is lonely in the ground."

Doesn't is just break your heart? What do you say to that?

Of course I felt I had to explain that there probably wouldn't be much left of Tilly and her fur to stroke because she was turning into a skeleton now, but my heart really went out to my little boy, who is just beginning to understand what death really means, even if it is only of a pet.

Oh, the joys of being a parent. I can only hope my rather clumsy explanations are not going to scar him for life.