It can feel like a steep learning curve, becoming a mum. One minute, you know precisely how to 'do life', the next you're in a state of 24/7 perplexity, trying to figure out precisely how this tiny little being you've created, you know, 'works'.

Of course, there are hundreds, if not thousands, of books and websites now to help first-time mums – between them all, they must offer every possible solution to every possible problem, so mums are bound to hit on the right answer sooner or later. One thing I never found any help with in my pile of baby/toddler books, though, was how to solve a problem like Cat.

You see, Cat wasn't your average cat. He was my little girl's invisible kitten, a friend she imagined one day, quite out of the blue, when we were reading a pre-nap story.

Ava was only two and a half at the time. All toddlers, in this burgeoning stage, are prone to crazy leaps of imagination on a minute-to-minute basis – she described what Cat looked like in minute detail. But what I wasn't expecting was for Cat to stay as long as he did. After Ava's nap, he was still there. At the end of the day, he was still there. After a week… yep, he was still there. Cat lived with us for months…though at the time it felt longer.

Ava is now eight years old and Cat left us a long time ago, but I have talked a lot about him in the last few years. Two questions I've often been asked are: 1) What was it like, having an imaginary friend in the house? And 2) Was it weird, how did you cope?

The honest answers are:

Mostly it was funny. It was certainly enchanting, watching a girl so in tune with her own imagination that she'd managed to create a kitten 'real' enough to actually act independently of her. So yes, I'd say it was 90% funny and enchanting. It was also 10% infuriating/maddening. No rushing mother wants to have to unstrap her only-just- strapped-in toddler from the car seat, so she can go back into the house to retrieve a forgotten invisible pet. And no mum wants to haul herself out of a relaxing bubble bath three minutes after she got in, because the invisible Cat had decided to get out of the bath, and was now shivering on the floor and needed a towel 'QUICKLY!'

2) Yes, it definitely was weird, in many ways. I didn't think twice about holding or talking to Cat when out in public with Ava. I expect I got some 'looks'. But that was the thing – when it came to 'coping', it was really more just a case of adapting. There was no arguing with Ava, you see. My instinct as a mum told me to go with the flow. Me telling my daughter that Cat WAS in the car with us would not, for one second, have convinced her when, in her mind, he was in the house, upstairs, on her bed. The fact that Ava sometimes tried to encourage Cat to do her bidding(extra rice cakes, additional bed time stories and so on), well, I wised up to that pretty quickly.

I never really spoke to my friends at the time, about Cat and his antics. I realise now I should have.

A quickly drafted question on my own Facebook page, about whether any friends' children had imaginary pals, returned approximately 25 'yeses' in the space of an hour or so. I was gobsmacked! All these invisible friends! All these mums, dads and grandparents run ragged not only by their own kids, but by invisible children, dogs, aliens…!

One thing that struck me: what all my parent-friends had in common was that they didn't find the imaginary friends worrying. Just like me, instinct had told them to stay cool, be patient, engage, and learn from the experience. According to the experts, that's precisely the right thing to do.

I asked a clinical psychologist, Dr Genevieve von Lob, about the right way to approach an imaginary friend who's moved in. "It's up to you how much attention you give to imaginary friends," she said. "But the best thing to do is to acknowledge and include them as a legitimate presence in the household.

"Be curious about this invisible visitor — and try not to dismiss them as non-existent, or figments of a child's imagination. You might even ask to speak to the imaginary friend, which may help you gain a greater insight into how your child feels, or reveal their perspective on certain issues."

Like many other (sometimes testing) aspects of parenting, even when we're required to step into an imaginary realm, it seems that mums, dads, grandparents and extended family do seem to just get on with it.

As Dr von Lob said: "Imaginary friends can, understandably, pose challenges – but they are a true expression of the magic of childhood."

There's no arguing with that.

Pip's book, Squishy McFluff: The Invisible Cat, is published by Faber and Faber and is available from Amazon.