There's nothing like sex to mess up a beautiful friendship - or so the nation learned from the classic dating disaster movie When Harry Met Sally. But did the film-makers get it wrong?
A new study of users of Friends Reunited's online dating service shows that friends can - like Ross and Rachel in TV's Friends - successfully become lovers too.
It also reveals that many daters actually end up becoming close friends with men or women they've been out with.
Rhoda Moore, Head of Romance at Friends Reunited Dating, said: "If one of your closest friends is a member of the opposite sex, and available, and you're looking for a partner, then this does seem the obvious place to start!
"But When Harry Met Sally casts a long shadow and many people don't take their friendship onto another level for fear of spoiling what they have.
"We wanted to find out whether dating really does spoil a beautiful friendship and also look at the reverse of the coin - the people who start out looking for love and end up as each other's best friends."
More than eight out of 10 (85 per cent) of the 2,000-plus respondents who currently use Friends Reunited Dating confirmed that the 'Harry and Sally Syndrome' really does exist. Just over a third (35 per cent) of the women and a slightly greater percentage of men (41 per cent) said their 'very best friend' is a member of the opposite sex.
Include 'closest friends' in the equation and the potential romance stakes are upped considerably, with three quarters of the daters confirming that members of the opposite sex are among their inner circles.
Interestingly, the survey shows that dating your friends is most prevalent among people aged between 35 and 55, showing perhaps that it takes both parties a while to summon up the courage to take the plunge.
In the survey, of those who said that they have close friends of the opposite sex, 56 per cent of the women and 65 per cent of the men said they'd considered dating them. About seven out of 10 of them actually went ahead and tried 'going out' with each other. Of these, a third are still in the relationship, a third have gone back to being friends - and another third aren't speaking to each other!
Asked why they had decided against dating their best friends, opinions diverged. A half of the women said it was because they 'just didn't fancy him'. By comparison less than 20 per cent of the men had any issue with physical attraction!
Around two out of 10 women didn't date their friend because they feared it would spoil their friendship and 33 per cent of the men felt the same way. Familiarity was the issue for the rest: around a third of both the men and the women didn't get together because, they said, 'we just know each other too well'.
Tellingly, asked 'what's more important - being friends or being lovers?', nine out of 10 women and eight out of 10 men said it was most important to be friends.
Rhoda Moore said: "It looks like a win for Ross and Rachel. There's only a one in three chance that if you date your best friend you'll spoil your friendship. It's just as likely that if it doesn't work out, you'll go back to just being friends - except now you'll 'always have Paris', or wherever!
"Best friend dating actually makes a lot of sense, because after all, deep friendship is at the core of any long-lasting romantic relationship."
They fancied each other - but decided to stay friendsTheresa Marchant (30, from Canvey Island), became best friends with Gary Attwood (34, from Rochester) after they met through Friends Reunited Dating. They started emailing in June 2004 and met in December that year. Their first meeting went very well - both were physically attracted to each other and felt the other was potential girlfriend/boyfriend material. However, with time, they became such good friends that they decided not to jeopardise their friendship by taking it to another level.
Theresa says: "Gary is like a male version of me! We bring out the best in each other and have so much in common. Gary and I chat every day, and I can't imagine my life without him. He's my best friend, I can tell him anything and we have great fun together. I know that Gary will be a life-long friend and it's not worth risking that for a relationship that could go horribly wrong."
From Friends to Lovers
Lucy Foxon, (30, from Berkshire) is now dating her best friend Adrian. They met at university and even lived together in student accommodation, but just as friends. After being close confidants for over 10 years they realised there was more to their relationship than just friendship and have now been going out with each other for six months. Adrian, who currently lives in Canada, is moving back to the UK to be with her.
The cautionary tale
Delia Churnin (27, from Edgware, Middlesex) dated her best friend Ben and now she doesn't speak to him.
Delia says: "Ben and I got on so well even though we were from completely different backgrounds and cultures. We met through mutual friends about four years ago and spent more and more time together, enjoying each other's company. Things came to a head and we crossed the line and started dating. Eventually Ben decided that this wasn't what he wanted and called a halt to it all.
"We have not spoken for two years now and I miss his company. I deeply regret crossing the line of friendship and I will always care about him."
Friends Reunited Dating launched in 2003 and is the UK's 5th largest dating site.
The site has over 400,000 dating members with around 1,000 new members, aged 18 to 80, joining the service every day - real people looking for genuine relationships.
It is free to register, anonymous, confidential, and comes at a fraction of the price of most other sites.