Most affairs start in the workplace, and a recent American study showed that women who travel for work are three times more likely to have had two or more concurrent sexual relationships in the past five years than women in general.But as well as seizing their chances, today many women and men plan their infidelities with chilling efficiency.'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.'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.'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.
'I went out and spent a fortune at Myla on gorgeous transparent bras and G-strings – things I'd stopped wearing for my husband, Peter, even before we were married.She uses specialised software to make sure her computer shuts down moments after she uses it and its history is wiped clean.She has two mobiles: one for general use and one for EMAs (extramarital affairs, to use the jargon), which can only be accessed by a pin number and is set on silent mode so that her husband, Brian, an events manager, can't hear texts arriving.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.