Last Friday I shut my laptop, closed my eyes and thought: 'Thank God for the weekend'.
As editor of an industry trade magazine, it had been a crippling week of deadlines with a two-day conference trip to Lille thrown in, and all I wanted was to get home and climb into the bath with a large G&T.
But as I pulled up outside my house, my heart sank at the familiar sight of my eldest daughter's Fiat in the drive.
She often pops over unannounced with my two-and-a-half-year-old granddaughter, Hallie. She's a single mother living ten miles away from us. I know life can sometimes be lonely for her, so she has a key that she uses to let herself in whenever she wants.
The thing is, it's not always when I want. More often than not, these visits happen at the end of the day when I'm exhausted from work and craving the solace of a quiet house. The last thing I feel like facing is the chaos of an overexcited toddler and a pile of plastic Duplo on my living room floor.
So I did something that could be viewed as mildly shocking. I kept driving right past the house and straight to the car park of our local pub, where I promptly turned my phone off and had that drink sitting in silence by the fire.
Am I hearing collective gasps of horror from grandparents all over the country? What kind of grandmother behaves like this?
Certainly if you ask a lot of millennial mothers, it's my job to help look after my granddaughter. Don't I owe it to my daughter to drop everything and help look after her offspring so her mental health isn't adversely affected? How self-absorbed and spoilt.
When Shona Sibary's eldest child, Flo, announced she was going to have a baby, she admits her attitude seemed un-grandmotherly, as she did not 'jump up and down with glee' at the thought of babysitting.
When Flo - the eldest of my four children - told me, aged 24 and in an already rocky relationship, that she was pregnant and going to grace us with our first grandchild, did I jump up and down with glee imagining precious weekends spent babysitting? I did not.
In fact, I'm not ashamed to say, I told her it was an inconvenient time in my life for her to have a baby - and if she expected hands-on childcare from me, she was going to be sorely disappointed.
My attitude may sound un-grandmotherly. But I'm in a different situation to most.
As people have children increasingly late in life, prospective grandparents are more likely to be retired, with endless time on their hands to chase after beloved toddlers.
By contrast, I'm 54 with a truculent 16-year-old (my youngest child, Dolly) still living at home. I have a demanding full-time job, two Labradoodles who need taking out three times a day and a husband who lives 4,000 miles away in Dubai. Where, I ask you, are the hours in my life to babysit my granddaughter?
I have - and often do - look after Hallie. I had her for an entire week when she was eight months old so that Flo could have a mini-break with her then-partner in Madeira.
We have taken both Flo and Hallie on a summer holiday with us twice, and Hallie comes to me regularly for overnights, insisting on sleeping diagonally across my bed, which leaves me about half an inch on the edge of the mattress.
I love it, of course. And I love them both. But I would be lying if I said I didn't often resent the imposition on my life.
I feel guilty viewing it this way, but the reality is that with four kids of my own, I've been parenting almost solidly for 27 years now. Just when I was seeing a glimpse of parole when my youngest leaves home in two years, suddenly there's another ball and chain clamped around my ankle.
Can anyone blame me for wanting at least a ten-year gap of not caring for other people before throwing myself into the martyrdom of being a grandmother? I'm just not there mentally. If anything, I need more time alone right now, not less, to recover from the ravages of bringing up four children. Quite frankly, even a year twiddling my thumbs on a desert island wouldn't cut it.
We've all seen that hilarious scene in the TV series Motherland where Anna Maxwell Martin's character, Julia, hammers on the door of her mother's house, demanding half-term childcare while the grandmother desperately tries to hide behind the sofa.
When I first watched that, pre-Hallie, it was with slight bemusement. Now, I'm totally there with her.
It's not Hallie's fault that she has a reluctant grandmother. And when she's old enough to read this, one day I will explain it's nothing personal. (Hopefully we can do this over a vodka martini, once I've taught her how to do the lemon twist).
Why it's a grandparent's JOB to help to look after their grandchildren and give parents a break
There are large chunks of being a grandmother that I am very much looking forward to. But who actually enjoys hanging out with toddlers? The ghastly soft plays, the relentless watching of Frozen (both films), the illogical meltdowns because I have cut up a fish finger the wrong way.
All of this I have done before with bells on. And the memories are near enough in my past that I haven't yet recovered from the PTSD.
Thankfully, Flo understands. Despite juggling two jobs and a toddler by herself with minimal help from Hallie's father, she is always grateful for any scraps of my time and luckily she doesn't view it as her God-given right to plonk her daughter on my doorstep at will.
Which is probably just as well. Because I have been known to sneak out of the back door and down the side of the house to escape. I've even, don't judge, hidden in the shed once so she thought I wasn’t in.
Am I the worst grandmother on the planet? Quite probably. But it’s a role that was foisted on me at a time when I want to put myself first for a change.
It was my daughter’s choice to have her child. So it’s nobody’s job but her own to look after her.