One of the challenges Sheila hadn't expected was where to hide her sexy lingerie.
'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.
It's about passion and spontaneity – having sex in the shower and up against a wall, all the things you see in movies that just never happen when you're arguing over whose turn it is to wipe the kids' bottoms.' The advent of email and mobiles have made affairs easier to run than ever before in practical, if not emotional, terms.
Yet suspicious husbands are also dab hands at checking their wives' inboxes.
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.
'Usually we just have a snog and a fumble but two have come back to my hotel room.