My husband Piers Morgan doesn’t want me to have male friends – because he’s convinced they want to have sex with me: CELIA WALDEN

“Of course men and women can be friends,” says Anna.

“No doubt about it,” Eden agrees.

“Men are the best friends,” Jenny emphasizes.

“They don’t judge,” Alice emphasizes.

“Or bitch,” Eden said again.

“Or have an agenda when you ask for clothing advice,” I say.

With a shocking combination of ‘yes’, ‘exactlys’ and the odd ‘so true’, all five women around the pub table celebrate this niche fact. It’s a sunny Saturday; a long, lazy girls’ lunch. But there’s an awkward silence, and I think I know why.

Celia with her boyfriend Dylan Jones, editor of the Evening standard

“I’m not really sure if I have many male friends.” Jenny is the first to come out. “Not really.”

“I don’t have that,” Eden admits.

‘None.’

The floodgates open and I suddenly realise that even I, who used to pride myself on having more male friends than female, don’t see them nearly as often as I used to. Earlier this year, I was also unusually stunned to realise that a man I kept seeing socially and desperately wanted to be my new gay best friend was not, in fact, gay at all – so perhaps that was asking too much of him. I had his number by then, and I still occasionally glance at it, my finger hovering over the ‘message’ button. Yet five months later, I still haven’t contacted him. Why?

I bet if you polled a whole group of British women, you’d find that male friends just aren’t really… a Thing. But since I’m not a gambling man, I contacted the authority on friendship for some statistics: world-renowned psychologist Robin Dunbar, author of Friends: Understanding the Power of our most important relationships. He confirms that when it comes to British women’s best friends forever, ’85 per cent are women and only 15 per cent are men, but these tend to be gay men or men at the feminised end of the male distribution, ie they are good listeners and not too dominant.’

And how weird, how wrong is that? Where are all our dominant heterosexual male friends who never let us finish an anecdote?

In the month since that Saturday afternoon epiphany (we call it a “pub epiphany” because that’s a Thing), I’ve done my own research into this overlooked and under-reported cultural blind spot. What I’ve discovered is surprising, funny, and sometimes downright sad. Most alarming was the initial debate over what counts as a male friend, with conversations generally following this line. “Male friends? Sure, I have loads. What do you mean brothers-in-law don’t count? And what about my husband’s friends? The guy who sits opposite me at work? He sometimes invites me to go to the pub with the rest of the team – when it’s someone’s birthday.”

Celia’s husband Piers Morgan

To clarify what we mean here, a real male friend is someone you meet alone on a regular basis. He is someone who despises the same people – real and famous – as you do (nothing bonds like mutual hatred) and is prone to sending you uncaptioned WhatsApp images of particularly idiotic things they have said, done or behaved.

Like good girlfriends, a male friend knows exactly how you take your martinis, that you like a table at a restaurant but prefer the bar, and that you can’t be bothered to watch the latest watercooler drama because it’s “not your thing.” So, basically, they’re husbands, minus the sex and the resentment.

Unlike female friends, they will never ask about your children (hallelujah!) or have to go home early to their own. Due to male blindness, they are usually unaware if you have gone through an ‘ageing cluster’ (a series of increasingly inventive forms of physical decline), which is always a blessing. They may fill dishwashers like meth racoons, but my god, men make great friends. So why do we exclude 49.45 per cent of the British population from our inner circles?

When I ask Professor Dunbar whether the dominance of single-sex friendships is partly due to single-sex schools and the single-sex mentality that always feels more widespread in Britain than elsewhere in Europe, he assures me that the problem ‘runs much deeper. We see it elsewhere: 75 per cent of women’s social networks are women, 75 per cent of men are men’, he says. ‘There is a strong homophily effect (we prefer friends who are similar to us). However, close cultural similarities (shared interests, moral or political views, etc.) can override biological differences (particularly gender, personality, age and ethnicity). We see the same thing in social monkeys and apes.’

If they can override these things, how come the monkeys in my stratosphere can’t? Are we back to the whole When Harry Met Sally riddle, where once even the possibility of sex is ‘somewhere’ the friendship is ‘ultimately doomed’ from the start?

After attending an all-girls school until she was 18, Jessica Fellowes, author of The best friend‘It took me a long time to learn how to be friends with someone of the opposite sex,’ she admits. ‘I basically assumed that if you liked them, you kissed them. I did eventually have a few guy friends in my 20s, but a combination of my boyfriends and their girlfriends tended to extinguish those, especially if one of us was single while the other was in a relationship.’

The theory that couples ban close friends of the opposite sex is echoed by a number of my female friends—and I can’t help but find it depressing that beneath our progressive, post-post-post-feminist facades, we seem to be stuck in a 1950s rut ​​on this issue. Two friends offered the following sentences: “My husband wouldn’t like it if I said I was having dinner with a man, even if it was platonic.” “I stopped seeing my best male friend a few years ago. My husband kept asking why I needed a male friend when I had one.”

Full disclosure: my husband doesn’t like me having friends of the opposite sex either. Like throw pillows, I’ve had to fight for every pillow I own. He’s convinced (like many men) that every heterosexual man is just using “the old friendship trick” to get into bed with me.

If you’re going to have male friends when you’re in a committed relationship, everyone I’ve talked to agrees that there are “unspoken rules” that you have to live by. A sort of boyfriend code. If the friendship predates your relationship or marriage, you’re allowed to keep it, but if you meet a guy tomorrow and want to have dinner with him, that’s pretty much out of the question. If you dated the guy ages ago and both parties are just sick of each other, go ahead: be friends. You’ve probably gotten all the sexual tension out of that relationship; it’s probably safe. If the guy in question is currently dating Gisele Bündchen, that friendship is also allowed.

I don’t like these rules. They feel like social corsets – uncivilized. I think the boyfriend code needs to be rewritten so we can all broaden our friendship horizons. There should even be a national “meet a random guy and make him a friend” day. Because aren’t we missing out on some of the most enriching relationships of our lives?

My daughter had a male best friend. When she was five, I walked into the bathroom and saw him sitting next to her on the cold tiled floor, chatting while she peed. It made me sad at the time that we can’t continue to have these kinds of friendships as we grow up. The kind of friendships that are so strong that they transcend even the most basic rules of etiquette, and certainly gender. Although a male bathroom buddy? I can’t imagine my husband would ever agree to that.

Celia’s latest novel, The squareis published by Sphere, £9.99. To order a copy for £8.99 until 1st September, visit mailshop.co.uk/books or call 020 3176 2937. Free UK delivery on orders over £25.