Popular culture is littered with examples of great love blossoming from platonic beginnings. But in real life, falling for your best friend doesn’t always go so smoothly.

It was supposed to go the way things do in the movies. Nora would tell her best friend that she loved him, he would feel the same way and then they would kiss – preferably in the rain. So when the 30-year-old arts manager declared her love for her best friend when they were still teenagers, she expected a happy ending. “I was so convinced that if you’re best friends and one of you starts getting feelings, the other person would match you." Sadly, that was not to be the case.

“I said: ‘I’m in love with you and we should give it a go,’" Nora remembers, “and he couldn’t really meet my eye. I was like: ‘Oh God, oh God, I’ve made a massive mistake!’" He said some kind words and let her down gently. Humiliated, Nora began to cry.

If there is one thing pop culture can agree on, it is that platonic friendship can turn to great romance – hence the genre-defining When Harry Met Sally, Ross’s mad airport dash in Friends and Ron and Hermione’s marriage in the Harry Potter novels.

“You see that trope again and again," Nora says. “They’re like brother and sister, then something magical happens and they start to see that person differently." But, in real life, things don’t always work out well. What is the best way to tell a friend you are in love with them?

Sit with your feelings for a while, advises Simone Bose, a relationship therapist at Relate. “If you are going to take that step, ask yourself: are you serious about this?" Look for signals that they might be romantically interested in you. “Is it an intense friendship? Does it sometimes feel like boundaries are crossed?" Clues might be if you keep touching each other, or avoid talking about sexual partners around them.

Nora wishes she had read the signs. “He hadn’t given me any indication that he was interested in me romantically at all, and friends had tried to say that to me very gently, but I wasn’t hearing it."

Keith, who is 61 and from Bristol, has loved a close friend for more than a decade, during which time he has even put her in his will – but has decided against telling her. “I love her to bits," he explains, “but I daren’t bring that up because it could unhinge what we currently have." He does his best to be philosophical: “Hey ho – we don’t always get what we want."

Perhaps he needs a “Cupid ". That’s how Janette Miller, 76, describes the man who helped her towards a very happy 30-year marriage. “Miles was 34 and I was 21; we met when we were learning to ice skate. Miles became my friend and dance partner for eight years. But, to him, I was just a pair of skates on legs. One day, our mutual friend Noel told me I ought to marry Miles. I said that he would be perfect, but he never saw me that way. Luckily for me, Noel had said the same thing to Miles – and Miles then started to court me."

If you are unsure whether your best friend may have feelings for you, Bose has a simple solution. “Flirt! Try and get a gauge on whether they’re reacting in a positive way, or if they look really uncomfortable." Be warned: the flirting may go over their head. When 28-year-old publicist Asher Alexander, from Barnet, asked his best friend, Rae, to the cinema, he thought it was clear he was asking her on a date. But his intentions were lost on her. “After the movie, I said: ‘Look, we should make this an official thing and date properly.’" Rae was so shocked she laughed in his face. Happily, she softened over time; six years later, they are getting married.

What you shouldn’t do is tell your friend you love them when you are drunk or high. “You can behave in a more emotionally catastrophic way," Bose warns. “Things can get out of hand quite quickly. So have the confidence to share your feelings when you’re sober." Keira, 28, learned this the hard way after confessing her feelings for her best friend after taking MDMA on a night out. “It wasn’t just like: ‘I’m high and I’m just saying this because I’m high,’" the editor, from London, clarifies. “I genuinely believed it at the time. I’d been thinking it for ages and blurted it out before I’d processed it." He responded positively and they made plans to go on a date. But as it neared, Keira started having doubts. “I’d think: ‘Do I actually fancy him? He’s a great guy, but I couldn’t imagine us having sex.’" So she did something she profoundly regrets: she ghosted him. “It is probably the absolute worst thing I’ve ever done to a friend."

Alex, 27, who works in the fashion industry, fell in love with his best friend. When they met in 2015, “it was love at first sight ". They bonded over everything – their childhoods, values and favourite photographers. “I connected with him in a way that I have connected with few human beings on this Earth." But Alex has never said anything. Why? Because his friend is straight. “There was nothing to be gained from telling him, because I knew he didn’t like me in that way."

Eventually, Alex had to take a step back from the friendship because it became too painful. He knows he made the right choice. “I believe he knows and, in my heart of hearts, I believe he did love me back in some way. He used to say I was like his soulmate, or brother – like a soul brother. I didn’t believe in love at first sight or soulmates until I met him. If there’s a platonic version of a soul mate …" He tails off. “The connection was very strong and very real."

Be mindful of how you transition from a physical relationship to a sexual one. For 31-year-old copywriter Tom, who has been in a relationship with his best friend for two years, it came easily. “The sex was totally mental and as soon as that happened we were both like: ‘Well, if we’re best mates and the sex is mental ... we’ve been inseparable ever since." But what if the sex feels awkward, like you’re kissing your brother or sister? “Go with the flow and what your desires are, rather than forcing it," says the sex therapist Miranda Christopher. If at any point it doesn’t feel right, take some time out. “Think about why it’s not feeling right. Focus on that feeling and ask yourself: ‘Am I just feeling nervous, or is it actually that I don’t really want to be doing this?’ In which case, you need to remember that they are your friend, first and foremost, and you should be honest with them and say: ‘It’s not feeling right.’"

When things go right, falling in love with your best friend can be magical. “I have nothing to hide from her," says Alexander. “I can be my most complete self, and open, and I never have to succumb to any of that bullshit toxic masculinity where I have to ‘be the man’."

The downside? “It can be claustrophobic," says Tom. “Sometimes we’ll be having a tiff and our group WhatsApp will go off and I see her respond to it – even though she’s ignoring my messages." Alexander has never been able to keep a secret from Rae, because she knows him so well. “She’s so good at reading me – from my tone of voice to my facial expression. It’s just really hard to keep things on the down-low. I don’t think I’ve ever got her a surprise gift without her knowing what it is a week before."

And what if the relationship doesn’t work out? In a word: communicate. “Say: ‘This is hard, but let’s work this out, because we want to be friends,’" Bose advises. “That can be tricky, because once you’ve gone over the line it’s hard to go back. But it’s not impossible." Ellen, a 26-year-old HR manager from Ashford, is proof you can transition back to friendship amicably. She discovered her love for her best friend like they do in the movies – by kissing him in the rain. (It was less cinematic than it sounds: they were drunk, waiting for a night bus and standing beside some bins.) After three years of dating, they broke up in 2016. “The passion had gone and it was back to us being friends again." As they both felt the same way at the same time, the breakup was frictionless. “Our friendship is still as strong. I can talk to him about anything at any time."