It's difficult to admit, but some friends see you as an acquaintance - and vice versa

Friendship is a complicated business, and it turns out that just because you presume you're in the inner sanctum doesn't mean you actually are

(Jason Alden)

I was quite surprised the other day to read in the paper that a fellow journalist described me as a “good friend”. I have yet to have a conversation with this person. So I emailed him – in a friendly way, of course – keen to catch up. He has yet to reply to my message.

Just imagine if you were the Pope, to whom this sort of thing happens all the time. People are constantly claiming Pope Francis as a friend, he admitted recently, with some sadness, in a radio interview. “Friendship in the utilitarian sense – let’s see what advantage I can gain by getting close to this person and becoming friends – that pains me,” he told the Argentine journalist Marcelo Gallardo, who is indeed an old friend of his. “Friendship is something sacred. The Bible says to have one or two friends.”

Yes, that’s true. But the Bible was written quite a few years before Facebook turned up. Nowadays, not to have at least three figures’ worth of “friends” reveals you as a bit of a social failure.

Maybe we should take more account of the Bible and less notice of our smartphones, because Facebook “friending” – and collecting mates on Twitter, Instagram and all the rest of it – is not really about friendship: it’s about being seen at the party. That can often be hugely entertaining, but it is not proper friendship.

Do you reveal your inner soul on Facebook? Of course you don’t. You save that for real friends: people you love to see in the flesh, in whom you confide your innermost fears, about whose life you care deeply. These are the friends whose successes you celebrate rather than envy, whom you don’t cancel on when you’re due to meet, to whom you never lie, for whom you would drive across the country, and whose partners and children you tolerate (you might even consider them friends too).

Of course, that friendship is not always two-way. The pain of realising that someone that you consider a “proper friend” actually has you down as an “acquaintance”, is intense. “I’m so sorry but I can only invite relatives to my wedding,” a “dear friend” once told me. Weeks later, she brought her photo album to the office. There she was, waving her bouquet with about five colleagues grinning alongside her. I had to go off and cry in the Ladies'.

So how many friends should you have? I think the Bible is spot on: both in the sacred nature of friendship and in its paucity. My dear friend Deborah famously used to “cull” friends every year, opining rather like Pope Francis that less is more. After all, you can only giggle with, take advice from and confide in so many people at once. So rather like the unworn clothes in her wardrobe going to the charity shop, Deborah would simply erase people from her diary whom she hadn’t contacted for years. Harsh, maybe, but friends from the school gates, or earlier jobs, simply fizzle out when the circumstances which first formed the friendship change.

But unlike clothes, you can’t drum up new friends on command. For a bond to form, they have to appear at the right time in your life, often at the start of new things – schools, jobs, child-rearing.

Nick Hornby once wrote a piece in which he described meeting dozens of people at a book signing. Although they all seemed as if they could have been brilliant friends, he observed, it was too late: by the time you are 50 – like it or not – you have probably got your friendships nailed down.

All of which means that losing them is exquisitely painful, because their wit and wisdom (and basic tolerance of your foibles) is irreplaceable. You can’t make real friends in weeks.

I have lost two great friends. Deborah, who died at 41, was one. Female friendship is celebrated in Miss You Already, a film which opens in London tonight. It is written by her lifelong best friend, Morwenna Banks. Two or three of us who also loved her dearly will go along, take boxes of tissues, and drink bottles of bubbly afterwards.

Having hundreds of friends on a tiny screen is fun, but it is not vital. Having a handful of proper friends with whom you travel through your life is something worth holding on to and celebrating.

As the Pope’s namesake, Francis Bacon, has been quoted as saying: “Champagne for my real friends, real pain for my sham friends.”