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.Subconsciously you're deciding whether you can take it further, from a friendship on to a more emotional and sexual level.' Of course, the overlap in what we want from both friends and partners is significant.
As we live in a time when many relationships seem doomed to end in a dosi-do of partner swapping, few of us hold out much hope of ever celebrating a golden wedding anniversary.
That's why trust is key to the transition from friends to lovers.
'I had no idea that Sophie's feelings for me had changed,' he recalls.
'After a few months of first meeting her I realised I was attracted to her, and as time went by my feelings grew a lot stronger.
The happiness in one country compared with another can be largely explained by six key factors…
[the first]: the proportion of people who say that other people can be trusted…' Ray Pahl, a professor at the Institute for Social and Economic Research at the University of Essex, agrees about the primary importance of trust.
'In our world the sheer struggle of two people trying to cope with everyday pressures and have a shot at a decent life is immense.
If they feel they are in it together and can trust each other to be supportive, that is extremely appealing.
Mo Kurimbokus, a relationship counsellor, says, 'Think of it like foreplay.