We were friends before you started dating
But, when probed further, one third said they secretly lusted after their male friends.
It seems that physical attraction is often a by-product of a cemented companionship.
Their judgement tends to be more reliable.' Sophie and Simon have now been married seven years and have just had their first child, Maggie Mae. 'I truly believe that because we were friends first our relationship has always functioned on a much deeper level, which is actually quite rare among couples.
It's difficult for me to define why it switched focus that day of the wedding, but, looking back, I think Simon was starting to get under my skin.
Yet not every close friendship will develop into the kind of romance that would give Danielle Steele a run for her money.
'It's the sexual chemistry that ultimately sends you over the edge,' states Christine Northam, a counsellor working for Relate. Each of us has a psychological make-up that has been moulded by life's influences and experiences, and most of the time we're not even aware of it.
All the time you're being friends, you're learning about each other.
It was at her boss's wedding that Sophie Holland decided, with stone-cold certainty, that she wanted to be next down the aisle. Simon, one of her closest friends for the previous three years. We'd stayed overnight at his parents' house, and I woke up and thought, "I am going to ask him to marry me."' Until then Sophie, 40, had worked alongside Simon, 44, in a fabric shop in Soho, London.
She'd found this affable, gentle man appealing as a shoulder to cry on when her succession of thrilling but chaotic relationships dissolved.
I'd go on dates with other men and find myself thinking about him, and once I joked that we should get together.
I suppose I was testing the water to judge his reaction.
He'd even sit with her in the pub and have a couple of warm-up drinks while she waited for a new date to arrive. 'On that day of the wedding, when everyone around me was saying how lovely he was, I suddenly thought they were right.