This whole new relationship thing is a minefield, especially as you get older. The average age for divorce is mid-40s, which leaves plenty of time for men with more sex drive than sense to start another family.
That isn't the cut-off point. You are just as likely to split up in your 50s and 60s. The kids flee the nest and, at an age when my parents were thinking of taking a cruise and getting a Collie, it's 'congratulations on graduating, and by the way darling, Daddy is starting a new life with Sheila from accounts'.
I know of what I speak, having been the old carthorse turned out to grass when my partner discovered he was still a stallion.
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He left me for someone not much younger and, though attractive, not so very much that I would rush off for a facelift. Thinner certainly, but she also likes camping and hiking. I'm not entering that competition.
We've worked it out now. We are the new blended family — three religions and five children between us, and with time, I've come to appreciate his new partner. As long as I don't think too much about the break-up, the crying on park benches, the agonising loneliness, the heartbreak and the shame.
Yes, shame. It's humiliating to be the cast-off. I was given the nice redundancy speech about how much I meant to him in front of all my friends, on my 50th birthday. Then he walked out. All I missed was the bloody carriage clock.
But that's all water under the bridge of ruined marriages now. In my new extended, thoroughly modern family we're all peace and love: communal birthdays, genuine hugs and generous, thoughtful gifts.
My ex came to my 60th last month with his new family and even got a mention in my speech, albeit with a slight sting in the tail. I'm not a saint! Sometimes couples work these things out and, if not friendship, at least civility is achieved. But it isn't easy and, over time, I've realised there are certain rules the leaver should follow . . .
Don't do a Ewan McGregor
Remember that Golden Globe speech, where the prattish actor thanked his estranged wife — "who always stood by me for 22 years" — and the starlet who's his new squeeze in the same breath? Ouch! The two women in your life can never be mentioned in the same sentence. "Here's to the old dear, she served me well and here's to lovely Miss Sparkling Georgeousness"? Good grief.
One wonders what Ewan was thanking the new girlfriend for. All she has done is fancy him for a minute. But, sure, that's right up there with sharing a life with someone for decades. Cheers.
It's not "your" home
Just as you don't co-mention, neither should you return to the old marital home after you've split. If you're invited in for a cup of tea after the dust has settled, be grateful. Don't act like you've just popped out to buy milk and slump down in your favourite armchair with your feet up.
The landscape changes once you no longer inhabit the same space. When my ex unwisely spent the night on the sofa on Christmas Eve and then used my hairbrush in the morning, I nearly punched him.
Stay blissfully silent
Never talk about your new squeeze to the old trampled one, and possibly not to your kids either. Even if goaded.
Nobody wants to hear about your new-found bliss, or how you felt stifled, or how 'it just happened' or how she can play the harp or indeed her skill in any department.
Do not be drawn, though we will attempt to draw you. We will want to know exactly what this other person has that we don't.
Or we think we do. Why are they better? What makes you prefer them to us? Where were you really when one of the children got a school prize and you said you were working? Don't tell us! Unless you want to take our hearts and scrunch them underfoot.
Time to shop around
While not being over-familiar in your former family home, you must also observe a strict exclusion zone outside it. Imagine your ex-family lives in a "safe" neighbourhood that extends as far as your previous life allows.
Everything you do henceforth must happen outside this area plus, say, a mile for safety. This is now their country, whose borders you may not cross unless invited and alone.
If you are found in the local Waitrose stocking the love nest's kitchen, expect to be run over with a trolley. Especially if there is champagne in your basket.
I did once run into mine in the cereal lane. I wanted to die. There's something so poignant about an everyday activity you used to do together that to then see this very domestic act done with someone else makes your soul shrivel.
He was only saved when I saw his partner buying All-Bran. Ha! 'Constipated,' I thought, and wafted away.
Never use the 'M' word
Never refer to your ex as the mother of your children. She isn't. Her identity is in no way linked to yours.
She is more than a walking womb that you availed yourself of as a way to procreate. She is the mother of her children, and will go on being so. She will continue picking up the slack, while you are swanning around in your shiny new life, trying not to make them hate you and encouraging them not to take your desertion too personally, because otherwise it will taint their lives.
She will do this because she loves them; for their sake, not yours. So don't expect to get the Father of the Year award, unless it's broken over your head.
"Father of my children" is okay for an ex-wife to say, however. Often, that is about all that he's contributed to their upbringing. Miaow.
Don't hog the friends
Don't go round telling mutual friends how much 'happier' you are now, as you hold hands over dinner with Miss Yoga Pants, or — God forbid — discuss the shortcomings of your previous relationship as a means of justifying your disloyalty. It will boomerang back.
"But," you say, "she's telling everybody how I left her!" This is true — because you did. Remember?
Accept that, in a divorce, you get left with the stuff you had before the marriage — this goes for friends. You can take those that predate the wedding, but you have to be generous with the ones you made together. In many cases, most will follow you. She won't be invited to another dinner party of the sort you used to both attend again. Because she's single. So you don't need to gloat.
Note to the new wife
The most important thing in every family that has been blended like a Nutribullet is for all the grown-ups involved to respect each other's children.
If the first round of kids are slobby, entitled anarchists who nonetheless open your fridge with alacrity and eat all your expensive cheese, do not comment. Just hide the good stuff and buy some cheddar.
Nor should you expect them to like you or you them. It's okay. Their own mother may not like them all the time either, but she will still take you down with a stranglehold if you criticise.
Kids are the no-go area you may not wander into without a happy smile and gritted teeth. Accept that there is history between the ex-wife and the husband and understand it was not all bad. This is no threat to you. You've got him now and you will make your own memories. But you can't negate the past.
Of course, you could argue, in turn, that the first wife really should treat your present set-up with careful respect, too. I'd steer clear of opening that can of worms, myself. But then, I was there first.