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Here’s a moment when I’m stretched out in a plank, balancing my trembling carcass on a moving, weighted platform that is poised to spring back in my face if I don’t hold it steady, when I wonder if I’m going to die. My spindly arms won’t hold out much lon

tough love bordering on masochism. ‘ You chose me, I didn’t choose you,’ he said at one point. One girl left in tears.

Like lots of LA trends and Ms Markle herself, the Megaformer has filtered over to the UK. So as I had basically forgotten the trauma from the first time, I signed up. Meghan has said, ‘Give it two classes…’ But perhaps not with a gap of years in-between. I spend the class mentally weighing up if death by Megaformer is preferable to the embarrassment of leaving halfway through.

Of course I battle on, too English to do anything else. But I take it down a notch the next day. Meghan needs running ‘as much for clearing my head as for keeping in shape’ and loves dogs. Running makes me wheezy and dogs make me sneeze. This is going to be a blast. I borrow a friend’s pooch and head out for Meghan’s standard six-mile jog, around my local common, not the Palace grounds. The effort of not losing the dog to a particularly menacing-looking swan turns out to be usefully distracting; as I gratefully hand her back, I clock that we’ve managed 5.7 miles. But I’m not sure what it did for my anxiety levels.

Promising myself more Californian zen, the following evening, around the time I’d normally be getting into my PJS, I haul myself out to Shoreditch, not for a drink, but a candlelit yoga class. A lifelong devotee of yoga – her mother Doria teaches it – Meghan’s said regular vinyasa practice is made better with hip-hop and candlelight. While she’s in LA she goes to the celeb-tastic Y7 Studio; over in Blighty, I’m off to Fierce Grace, favourite of our own TV royalty, Caroline Flack.

As I push the door open, I see I’ve made a catastrophic faux pas – clothes. My fellow yogees are in bra and pants; men in the briefest of shorts. I’m late, so I’m forced to take a front-row slot beside a man who looks like Sting’s sweatier, bendier and more scantily dressed doppelgänger. Thank god the lights are about to dip.

Over pounding, womb-like drones, our instructor breathily instructs us to go deeper, open our legs wider, experience the sensation. Yikes, is this what Megs gets up to? Does the Queen know? I tuck my top into my bra to increase airflow, and desperately suck on my water bottle in mild, rising panic as it gets hotter and hotter. Then something happens. The drones, the heat, the bendy man making impossible shapes… I feel spacey. After two hours I emerge into the night with sweat-soaked leggings, mascara-streaked face and eau-de-somebody-else’s-gymmat clinging to my pores.

The next morning, feeling stiff but high on love and peace, I hop out of bed at the first whimper of my daughter, hand her to my butler (aka husband) and head off to my first sound bath. I’ve read that Meghan meditates a lot, while I can barely close my eyes without my mind wandering. But as the teacher packs away her crystal bowls after my session at a newly opened studio in West London, I realise an hour has slipped by. I’ve either been meditating or snoozing, but I feel amazing. I glug down a spenny green ‘performance’ juice by Botanic Lab to seal the deal.

But deep down, I know this is getting too easy. My stalking had revealed that Meghan had a personal trainer in Toronto, so I book in with PT Matt Roberts, who has trained supermodels, actresses and MPS. Can he give me a princess-in-waiting workout? After a brief confessional – yes, I eat carbs; no, I don’t go to the gym much – he prescribes weights. Nothing flimsy: Meghan probably uses heavy ones four to five times a week. He drills me: deadlifts, glute bridges, fly presses, seated rows, followed by box jumps, burpees and skipping. Bloody hell. Behind that perfect smile is a woman made of pure steel. Me? I’m a beetroot-faced mess who needs help getting downstairs to the changing room.

Roberts offers to set me up with his inhouse nutritionist, but no need! From my notes I know that when it comes to down time – hello, weekend, I’ve never needed you more – Meghan loves to relax with a glass of wine and some chips. I don’t think I have the energy (or money) to ever repeat this week, but raising a glass to our newest royal? That I can do. To the bride!