Romy hated herself for it, but she found she couldn’t stop as the poison drip-dripped onto the fabric of their marriage, burning small holes at first, which soon joined up into huge jagged ones, until she felt there was nothing left but tatters. She had finally lost the strength to hold the fabric together.

And Michael obviously felt it. She’d sensed him pulling away from her over the previous thirteen months – spending ever more hours at work – at the same time as she had taken a step back from him. But distance only spawned more distance, with neither able to talk about it. The moment seemed to have passed when she might have spoken, Romy realized.

By tacit consent, they stopped entertaining – even for networking purposes – and he moved into the spare room: ‘I don’t want to wake you when I’m home late,’ he said, although he’d never cared in the past. Romy, in turn, began to make social arrangements with her friends, leaving her husband out of the equation altogether. They became like polite strangers, gliding past each other with only the briefest of acknowledgement.

On the rare occasions when they sat round the table together as a family, Romy would search Michael’s face, check how this uneasy domestic arrangement was affecting him. But all she saw was a guarded acceptance, and a titanic effort not to meet her eye – Just in case I mention the unmentionable, she thought sadly.

But it seemed as if there were light years between Romy’s first thought that she might leave her husband and deciding actually to do so. The prospect – which daily tormented her – made her feel physically sick. It wasn’t until six weeks after the incident with the Mulberry bag, on an icy January morning, that she finally plucked up the courage and confronted Michael.

The moment had been planned for – over and over – in the preceding weeks. She would lie in bed, stomach churning, telling herself, Today’s the day, then for some reason – Michael would leave early, she would oversleep or simply lose her nerve – he would be gone and she still hadn’t said a word. Which proved both a temporary relief and a cause of weary frustration with her own cowardice.

The Wednesday in question she had no plan. She’d been up early, working on the mission statement for a friend’s charity, which was raising money to save a large area of wasteland in East London that had been colonized by rare birds. When she heard Michael moving around, she had known this had to be the moment – it was days since they had spoken, she realized, even to say hello – but the tension remained. The shilly-shallying had to stop. She positioned herself in the hall, by the entrance to the kitchen and waited, holding her breath, her whole body rigid.