Why having a family holiday with my ex left me simmering in a cocktail of grief, betrayal and guilt... As Canadian PM Justin Trudeau and his estranged wife say they're taking a summer break with their children

So the Trudeaus are separating. Canada's first couple are calling it a day after 18 years of what everyone thought was blissful brunette matrimony. 

But wait, like the thoroughly nice couple they are, the prime minister and his wife, Sophie, are going on one last holiday together with their children, Xavier, 15, Ella-Grace, 14, and Hadrien, nine.

Not only that, but, going forward, they plan to co-parent by keeping the marital home in Ottawa as the base, even though they are no longer together — a concept that is known as 'nesting', apparently.

Maybe they are already off on a fortnight in sunny Cancun, or on one last wholesome camping trip in the Canadian wilds, but if they're still at the planning stage, or even the packing stage, I have some hard-earned advice: Don't do it!

I wouldn't say my ex and I had the most stress-free divorce. But we were still living in the same house for six months after he decided to leave. And if that wasn't bad enough, we also did what we then considered was the sensible thing and went on holiday together. Not once, but twice. Like the first time wasn't difficult enough.

If they're still at the planning stage, or even the packing stage, I have some hard-earned advice: Don't do it!, writes Marion McGilvary

The first time was just before he moved out, when things were on the skids, and the second time was a year later, by which point only two of our four children were still living at home —the others being at university or on a gap year. We also did Christmas together — twice. And believe me, this way madness lies — literally, in my case, but that's another story.

Let's stick to the godforsaken excuse for a holiday. Yes, it had been booked and paid for. And I was stupid enough to think that maybe some time away under the Sicilian sun would perhaps be healing and pull us back into yoke together.

In our case, the ostensible reason for our impending separation was my ex's assertion that we were 'broken'. I certainly was. Our marriage was about as far from perfect as DIY rhinoplasty, and no less pain-filled — but we had four kids and my ex was my rock, despite all the problems we had being in the same room together.

Splitting up felt like an impossibility, so I was clutching any straw I could grab, while, and let's be honest here, moping around like the West London version of a weeping Madonna, gazing off into the Mediterranean sunset remembering past happinesses, weeping into my Campari soda in the town square, while attempting a brave smile every time the kids looked at me.

Frankly, I would probably have left me too, such was my martyrdom.

Meanwhile, the ex, who had always hidden behind a newspaper at every opportunity, continued true to form, while playing the part of unusually reasonable parent. 'Yes, you can go to the next village with those teenagers you met on the beach. Sure, I'll send you in a cab.' Meanwhile, I was freaking out and looking borderline insane at the very idea.

He spent the two weeks playing good, reasonable, permissive cop; I was the spoilsport, the ineffectual disciplinarian who was also attempting to be the sweet-natured wifey (something that does not come easily to me, especially in the process of being dumped).

Like Justin Trudeau, he wasn't leaving me for someone else. Oooh, no. We just didn't work. But we'd always be close. He would always love me. I was the mother of his children, blah blah blah, and he still called me 'darling'.

In retrospect, it sounds highly dysfunctional, but as far as we were concerned, it was us being civilised, adult and responsible; caring even.

Mr Trudeau announced he was separating from wife Sophie after 18 years 

However, it is not easy being caring when you are feeling 50 per cent distraught and 50 per cent as bitter as unsweetened lemonade. We'd be having a nice conversation, a nice bottle of wine, in an idyllic restaurant, and I'd suddenly feel this surge of anger that I could barely contain and I'd want to smack him. Similarly, I could feel his lack of patience with my dying duck act, which stirred no sympathy in him, merely more anxiety to actually leave.

Then there were his long, solo walks which elicited a sigh if I wanted to accompany him. The obsession with wifi, and the laptop hurriedly consulted at every conceivable opportunity, which made me dog his every movement in suspicion, sticking to him like a wet shower curtain whenever he checked his email. I mean, of course there was another woman. It just hadn't been confirmed.

It's hard to play nice when you are simmering in a cocktail of grief, betrayal, shame and guilt. Heck, family holidays are a trial even when you are not getting divorced.

By the following year, things had settled down into fake happily-estranged family mode. He had moved into a flat with no spare room, and I'd taken a lodger to stop the house from feeling like an empty shell as, by then, I was home alone with just our youngest, who was in the middle of her 'hating me' period, which lasted for several long, painful years. She adored her father and when he left, I was the stooge she got to kick at every opportunity.

An unhappy tween is like living with an angry snake. I was covered in bites. But it was understandable. Her dad took her for dinners and on shopping trips; I got the eye roll and the silent treatment.

So why go on holiday together again? And why go to a wedding in the U.S. a year later to painfully watch another couple pledge their love to each other? Ditto why put on a brave face to visit family friends and share rooms (albeit in girls' and boys' rooms), and lock yourself into yet more trips where you act like you're still a united front when you're actually as divided as Korea?

Justin Trudeau with his wife Sophie Gregoire Trudeau (left) and their three children (left to right) Ella-Grace, Xavier and Hadrien

I think the moment I realised the idiocy of it all was when the ex idly reached for my hairbrush and began to use it, and I slapped it out of his hand. There are lines you just can't cross, no matter how much you long for togetherness.

Why have your ex over for Christmas and do all the cooking, all the cleaning, all the preparation, and have him swan in half-way through the day to the peals of joy from your kids saying, 'Yeah, now Christmas can begin!', when you're the one who has been up since dawn baking a chocolate sponge village complete with icing sugar snow, and wrapping those last-minute presents?

It was when my ex demanded that I drive him back to the flat that he was by then sharing with the girlfriend, who had, of course, been lurking in the background all the time, that I finally threw in the towel. Sod this, I thought. I'm not your wife, no matter how many 'darlings' you add at the end of the sentence.

So we no longer holiday together. We may meet for the odd family birthday and, in fact, are now, almost 15 years later, truly just like family with each other. We get cross, we make up, I ask his advice sometimes, I ignore it as usual.

He has moved to the U.S., to a house about a two-hour bus ride from the nearest airport, so relatives visiting isn't on his list of priorities. And he has another daughter, who will soon be old enough to give him the stink eye and ignore him. Smug? No, but I can't say the idea of him having to live through the terrible teens doesn't fill me with a little bit of glee. You know, a teaspoonful.

He has told me I should visit them. That will never happen. Though we have agreed that if there are to be any big family reunions in Europe with all of the kids, then I would get the option to join them, in a separate apartment, of course.

All these years later, what can go wrong? On second thoughts, don't answer that.

So, yes, I can understand why the Trudeaus want to keep some sense of family alive, even in the midst of separating. And, golly, I hope it works better for them than it did for me. And maybe they can, as they hope, 'remain a close family with deep love and respect for each other'.

Perhaps they have been living fairly separate lives for years while still cohabiting. Let's be real here, lots of couples are in that situation. Sometimes it takes one or other to meet someone else, to make them take the final exit train.

Habit is the killer of many marriages, and being in the public eye as well as part of a political dynasty comes with its own baggage.

Notably the last Canadian prime minister to divorce while still in office was Justin's father Pierre — from his mother Margaret.

So a holiday en famille when they have decided to part may not be that much different from any other holiday when both parties are disengaged and drifting apart.

Mr Trudeau and his family attending the 38th Annual Vancouver Pride Parade in 2016

Interestingly, it was the Trudeaus' anniversary earlier this year. Justin tweeted a picture of the couple holding hands in a campervan with the tagline: 'Every mile of this journey together is an adventure. I love you Soph.'

It might seem a tad odd to have gone from that anniversary message to separation in just a few short months, but at my 50th birthday before we split, when things were rocky, my ex stood up and made a speech about what a fantastic, beautiful, talented woman I was, enumerating every single article I'd ever written.

In retrospect, it was more of a CV than a tribute, but since he wasn't a man who ever said anything nice about me in public, I was immensely touched and thrilled. I thought it meant we were back on track. However, three weeks later, he told me he wanted to leave. He was actually giving me my retirement speech. I should have received a carriage clock and a golden handshake.

The next chapter in the Trudeaus' journey will no doubt be taken apart. Maybe I'm a romantic and think that their trip this summer doesn't mean the love isn't there at all. It's just no longer enough.

It took us about 12 years to get divorced. Honestly, even with all the angst and the humiliation, we were more happily married those years than we were in the previous 12.

It's not the end of the world coming to terms with the end of a marriage, if you can manage to renegotiate the terms.

We still have a lot of love left for each other, and when I meet up with my ex, he still tries to hold my hand. I tell him to quit it, in more florid terms. Then we laugh.