I ended up stuffing all my new buys inside the legs of a manky old tracksuit.I washed them by hand, locked in the bathroom, and dried them with a hairdryer as I didn't dare hang them up.' Tall, strong-featured and dressed in a cashmere sweater and wool trousers, Sheila is the kind of woman you see in the aisles of Waitrose, the front row of the school carol service.
Instead they are searching for variety in an otherwise humdrum routine. 'Traditionally we believe a woman who has an affair is looking for emotional intimacy, whereas men are looking for sex. 'Women feel more powerful and in control and as a result there are certainly more women being unfaithful because they fancied somebody and were away for a weekend with the girls or on business and seized an opportunity.
Or it's a case of a woman being neglected in the bedroom in the way a man once was and wanting to find a way to scratch her itch.' For a wired generation, the automatic place to turn to for satisfaction is the internet.
'The problem was where to keep them and how to wash them?
I could have worn them every day but after 13 years of greying M&S pants and flesh-coloured bras Peter would have been rightly suspicious.
'We have sex, we chat, we go back to our families,' Sheila tells me over a cappuccino.
'I'm not looking for a soul mate, I'm looking for physical release. The girls were small and sex with him had long been just another chore, like loading the dishwasher.
They had a much freer sexual history when they were single and they have far more expectations of good sex.
Of course, once they're married it doesn't carry on being like in the magazines but their copy of Cosmo is still popping through the door every month shouting six new ways to heighten orgasm tonight and they think, "It's not going to be with him indoors, he's exhausted, but what a lovely idea …"' Once the seed is planted, outlets are everywhere.
'Usually we just have a snog and a fumble but two have come back to my hotel room.
It sounds dangerous, talking about it like that, but I trust my instincts to know who's safe and who's a serial killer.
'They probably did online dating when they were single, so that's where they'll immediately head to see what's out there,' says David Miller, who runs Loving Links, an online dating service and one-to-one introduction agency for 'nice, middle-class attached people'.