I'm cheating. This column is a cheat. I should be doing something else. Instead, I'm doing you.

It could also be a cheat because it isn't me at all. Maybe it's written by Rachel, the editor, who's fed up with chasing Unc Func for his perverse id and dribbly views. So stuff it – she's just decided it'll be quicker to make it up herself, and actually say something useful for once. No, it really is me. Honestly. Trust me. Would I ever cheat on you?

Cheating is the most common subject of letters to this page.

"Cheat" has two meanings: to break the rules of a game and to break the faith of a partnership. It's interesting that the second definition has grown from the first, and it implies that love is somehow a game. A game with rules. What's the only other thing that all games have? Winners and losers. So that rather implies that in love there is a winner, and presumably the winner is the most talented and skilled at it, and perhaps the luckiest. That may be what we mean by "lucky in love".

But if you lose at love, more likely than not it's because the partner, or opponent, cheated, so cheating is actually the way to win. But that's obviously not right. So I'm going to merge all the letters into one, which is like cheating on a lot of people at once.

Let's kick off with Evangeline, who wrote simply to ask, "Is kissing cheating? My boyfriend says it is and if he ever caught me kissing another guy it would be grounds for throwing things – punches, vases, hissy fits, toys, prams – but, truthfully, I think that sometimes kissing's just a dance move."

Evangeline has touched on what is the essence of cheating. If you think of love as being essentially naked rugby, then you need someone else to decide what's a forward pass and a high tackle. And what was just exuberant gamesmanship.

Actually, when you're in love it does feel like naked rugby but then you're only allowed to tackle the same person over and over. Different people pull out a yellow card at different things.

Trevor for instance, who wrote last year and is probably in some sort of locked facility by now, asked me to back him up when he insisted that his girlfriend wore a full veil and chador when going to the pub.

It was the pub bit that interested me: what was a conservative Muslim doing taking his girlfriend down the rub-a-dub? It turned out Trev was a practicing "don't know, don't care". He just thinks that veils are a really good idea and that, actually, preferably, girls should be kept in hessian sacks because they're all nympho bitches who'll blow tramps on park benches given half a chance.

Bill Clinton from Washington famously didn't think that a blowjob was cheating, and Emma from Pinner says she feels cheated if she finds her husband masturbating. "That should be mine – all mine," she says.

But Sylvie from Newcastle says she doesn't mind if Chuka has one off the wrist as long as he's thinking about her, which he swears, absolutely, on his life, he does every time. I would have printed photographs of Emma and Sylvie, which they included in their emails, but we couldn't have got anyone to advertise for the next three pages. There are men who think that prostitutes don't count as cheating, or that having gay sex with strangers – as long as they're tops – counts as cheating.

Arnold, 75, wrote to say he'd just left Helen, his wife of 45 years, because he caught her holding hands with the octogenarian next door.

He pointed out that sex had not been an issue, or indeed a possibility, for any of them for a decade, but that the intimacy of holding hands seemed to be the most terrible betrayal, adding that, if they'd been younger, they might have got over it with the thought of the years ahead of them, and that the memories might have been buried in time. "But realistically," he said, "we're down to the wire, and are unlikely to move on. There's nothing we can do to make it better."

So he's off to an old people's home.

This is the trouble with cheating: there are no acceptable rules, or laws. It could be a smile, or dancing to a song that you considered to be indefinably "ours". It can feel like cheating to go to a restaurant that you used to go to with someone else. Keeping photographs of exes can infuriate, like retrospective cheating.

I don't have a definitive answer to any of this, but I would say that it is easier to work on your own jealousy than police somebody else's behaviour and thoughts.

The worst culprit for cheating is the mobile phone – sexting, texting. Most people who cheat do it on the phone, and they all get caught.

My only piece of advice is that all of you consider every single text and Snapchat that you ever make as also being shared with your partner, because they all check your phones all the time — trust me on this one. And if you don't trust me, then trust yourself because you look at your girlfriend's texts when she goes to the bog like everyone else.

Here's a letter I got last week. It doesn't warrant or ask for a reply – it's just a story – but I thought you might like it.

Bob had a row with his brother. A big row, in the course of which his brother told him that he was in fact the father of Bob's only child, a daughter, who is now 18. Bob is still married to his wife. He said the news was devastating. "I went for a walk. I came back after an hour and I sat my brother down, and quite calmly, I told him to consider who'd been cheated in this relationship. I'd had a daughter, who I'd shared Christmases and holidays, homework and bedtime stories with, who I taught to ride a bike and bought her first car, who brought her boyfriend home to see me. I had a wife, we'd made a life together, and a home. He'd had sex with someone else's wife but never managed to find one of his own, and he had a niece who thought he was a bit creepy. And he used to have a brother who looked up to him. Which one of us had life cheated?"

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