If I crane my neck, I can catch a glimpse of them together in the restaurant. I peer under the rear-view mirror, my full view of him impeded by the 'L' of the Lorenzo's sign. I've been here for 23 minutes and their starters have just arrived. I tut: Lorenzo's standards have been slipping recently. Last week, I had to wait 30 minutes for a simple dessert.

He edges into my line of vision as he sits forward on his chair. He raises his hand and cups her chin. She looks down in a mannered, practiced way like a little girl in a school play. He'll like that. I imagine his eyes twinkling, sparkling their special silver. The handbrake is pressing against my thigh. I'll probably bruise – I'm fragile like that.

They've ordered oysters I note with a sinking heart. I watch his familiar hands, hazy in their rapid movements, lit by the candle, as he prepares one for her. She's still looking shyly at the table-cloth. My God, she must be in her early twenties. I feel myself flush with anger.

He whispers something to her and she looks up through her thick, dark lashes. I watch her nod, her mouth form a shy little smile and then open, wide. He's watching her, mesmerised. He lifts the oyster shell to her mouth, their gaze locked. He mimics her, his lips slightly parted as he eases the shell onto her lower lip. With a swift, slick movement of his sharp, silver knife, he shucks the oyster into her mouth. I imagine rather that see the smooth gulp as her throat constricts. I close my eyes, my own throat tight. I swallow down the bubble of hurt.

When I open my eyes, I see that he has moved back in his chair and out of my line of vision. She has resumed her submissive table-stare again. I note that her palms are flat down on the table. This must be a new part of the game. He edges into view, tilts her head up, whispers in her ear again and her mouth opens automatically. Oh she's good, I think. His large hands cup the next shell while his long fingers work the knife like a master. Her head tips back, and this time he places his flat palm on her throat, feeling the oyster make its downward journey. I think I'm going to be sick.

A rap on my window makes me jump.

"You can't park here," a voice booms its warning, the speaker's face distorted as it looms toward my window.

I nod my agreement, desperate not to make a scene – he'll recognise my car. With a shaky hand, I turn the key in the ignition and hear the smooth hum of the motor. The uniformed man steps back, an admiring nod at the car. I rev the engine to show its power and roar off into the night, my sight slightly blurred by hot, hurt tears.

I park in the underground garage and pull off my wig. It's made of real human hair and makes me a blonde for the first time in my life. I place it carefully into my glove compartment and run a hand through my own light brown hair. I'm not looking well I realise as I face myself in the mirror. I'm tired and I look it. Small, black rings darken the hollow under my eyes, my skin looks a little tired. I squint in the half-light of the garage, not flattering myself any. I sigh and open the door, grab my bag and head to the elevator.

The elevator pings my arrival at the Penthouse, our house. The apartment is quiet. I step out of my heels and tiptoe down the hall, feeling the thick carpet's caress on the soles of my stockinged feet. I flick on the unobtrusive lamp on the side-board and head for the bar. I've been drinking a lot lately. I unscrew the top off the brown apothecary Hendricks bottle, and glug a few shots into a glass, dispensing with the slice of cucumber. I don't have time to cut it. I need it to work, fast. I add a splash of tonic and retreat to the leather armchair that overlooks the city. I swirl my drink around already calmed by the fizz that escapes. I sip and look out over the skyline, the lights comforting like old friends. What the hell am I going to do?

After my third refill, I stagger to the bedroom, my hands already unbuttoning the silk-covered buttons of my light-grey shirt, a shirt he has bought for me. A soft whimper escapes me and I jerk my head at the odd sound I have made. I peel the shirt off, and slam the light on so I'm standing in rather bright light in front of the mirror. A forty-year-old stares back at me, swaying in her tight pencil skirt and bra, hair wavy and slightly wild, mirroring the look in her eye.

"That's me," I whisper and lurch forward so my reflection and I are eye-to-eye. "Me," I say again, trying to understand how I got this way, when and how I grew up. My hot breath fogs up the mirror. This is not the first time I have had these tet-a-tets with blurry-mirror me. They started a few years back but their frequency has increased of late. In my head I'm in my twenties, stalking around, capable and confident in that way that only the young truly are. Then I'll catch a glimpse of myself, in a shop window, in a passing taxi, and I'm shocked that my outer shell doesn't correspond with the inner core of me.

I'm still beautiful I'm told, often, by many people but since I've never really felt that I was, it's hard to believe it now. He says that I get better with age, like French cheese. I'd hit him with a pillow when he first made that analogy, and giggled – his favourite sound – and allowed it to become an 'in' joke. Even now he gives me a wink when he orders a cheese-plate at a restaurant.

I unzip my skirt, and shimmy it down my thighs, a provocative, drunken smile at myself in the mirror. I flick my hair as I dispense with my skirt, throwing it behind me so it thuds, softly on the bed. He used to love this game, this dance and I used to love to perform it. It also used to be enough.

I still work out to maintain my slim frame and have found over the years that I need to exercise every day. And I have to watch what I eat. He used to control that, would ask me constantly if I had eaten, check up on me. It showed his love. Now I can skip entire meals and he doesn't even notice.

I cock my head to the side and assess myself, standing in expensive lingerie that I have picked. You should be dressed in silk he used to say. He knows my body as well as I do, has explored every inch of it over the past 20 years, has claimed it as his. It's as familiar to him as his own. And therein lies the rub.