Two years ago she and Peter, 71, celebrated their golden wedding anniversary with a trip to the Grand Canyon and a party for their close friends and family.
For Sarah, there was no single climactic moment of crisis.
'For the past ten years of our marriage, our relationship had been breaking down,' she says.
He says: 'I'm happy to carry on as we are, just chugging along. We've got what we have today through hard work and partnership: she's done all the brain work and I've done the muscle. 'I've um-ed and ah-ed about this for years, but I'm done with the dutiful wife bit.
I thought we'd grow old in this place with the family around us.' But Margaret has other ideas: 'I managed to put up with it until he retired, but it's been worse since he's been here all the time. I've done it for too long.' They met when they were both living in London and Margaret was still at school.
A deliberate ploy to make the viewer think something sexy or illicit is occurring when it actually is not.
A scene will begin with its characters not visible to the camera, or partially obscured; the dialogue between them seems lascivious and explicit, or be laced with double entendres.'He only had a week's leave and then he went away for six months. Neither of us had ever had sex with anybody else so we learnt about it together, which wasn't very much; sex was never brilliant.But the children came along, and you wouldn't dream of leaving when you had young children.' Now, though, as with so many other couples, the children are long gone and Margaret finds she has nothing in common with the man who has shared her life for so long.He took no interest in me or in what I had to say,' says Sarah who now lives alone in the three-bedroom house she bought with the proceeds of her divorce.Many couples of a similar age share Sarah's sentiments.But the situation is often so distracting it's hard to notice at first. I know it's cruel, but if he can't manage it tonight then he's for the choppy-chop.