It's one of the most poignant and beloved of romantic tropes - a couple who starts out as friends, but love blossoms between them. Clearly, Dame Joan Collins believes in it too, as that's exactly how her and husband Percy Gibson's love story began.
The 90-year-old star, who has had more than her fair share of trials and tribulations in love, recently opened up about her marriage to Gibson, her fifth husband since 2002.
In an interview with the Mirror, the Dynasty star described Gibson, 36, as a "wonderful, kind, truly good man" who is her "accomplice and best friend".
Elaborating on how she and Gibson's romance came to be, Collins said: "Percy and I became really good friends first. So we had this connection. We really knew each other."
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Other celebrities who took their friendships into romantic territory include Rihanna and A$AP Rocky, and Jamie Laing and Sophie Habboo.
So it's clear that the transition from friends to lovers can make for a successful relationship. But if you have an inkling that your best mate might just be boyfriend material, what can you do to make the change? And should you?
Why do relationships that begin as friendships seem to be more successful?
According to Limor Gottlieb, doctoral relationship researcher, science is on the side of friends-turned-lovers. Some research suggests that relationships that start as friendships "tend to be more stable and satisfying", she says, pointing to a 2012 study published in the Journal of Social and Personal Relationships that found that couples who went down this route reported higher levels of satisfaction and commitment.
She tells Yahoo UK: "There are some explanations for this. For instance, friendship is built on trust, open communication, and emotional intimacy so when a romantic relationship evolves from a strong foundation of friendship, these elements are already in place, which can contribute to a healthy and enduring partnership.
"Going from friends to lovers also means less pressure and anxiety about having to impress the other person. In healthy friendships there is also a strong foundation of mutual respect and providing emotional support and a safe space for sharing feelings and thoughts, which is crucial for successful romantic relationships. It is also important for romantic relationships to progress gradually and provided the transition from friendship to romance is gradual, it can lead to more stable and lasting relationships."
Barbara Santini, psychologist and relationship adviser, adds that such couples have built intimacy that isn't purely physical, which ensures their attraction won't fade as bodies and looks change. She says: "Emotional and intellectual intimacy often grows stronger with time. Couples who've been friends first usually have a profound level of non-physical intimacy, which can sustain the relationship even during challenging periods."
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Are there risks involved?
As with any relationship, there are always risks. Santini says that "idealising" a relationship can threaten to ruin it, explaining: “Friends often see each other in a non-romantic light. When the idea of romance sparks, there's a tendency to idealise the other, which can create unrealistic expectations. Being aware of this trap allows couples to approach the relationship with a balanced perspective."
Gottlieb adds that there is a chance a romantic relationship might not work out, which could also spell problems for the friendship underneath it.
"Some people can return to being friends, while others may find it more difficult. If you share the same group of friends, a breakup can potentially affect the dynamics of the entire social circle. Research also shows that some people may be motivated by sex to enter romantic relationships with friends, so it's important to discuss these potential risks and challenges openly with your friend before deciding to pursue a romantic relationship."
Should I do it anyway?
Before you jump into a relationship with your best friend, there are a few things to reflect on.
"Be honest with yourself about your intentions," Gottlieb advises. "Another tip is to 'read the room', meaning try to get a sense if the romantic feelings you experience are reciprocated. Signs to look out for can be increased physical touch, flirtatious behavior, or expressions of emotional closeness.
"However, keep in mind that these signs can be ambiguous, so it's essential to communicate openly. Honest and direct communication is key. You could say something like, 'I've been thinking a lot about our relationship, and I've come to realize that I have romantic feelings for you. I wanted to share this with you and see how you feel'."
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But once you've initiated this conversation, you must prepare yourself for any answer, even if it isn't what you want to hear.
"If they don’t share the same feelings, it's essential to continue valuing the friendship and not pressure them into a romantic relationship. But if they are interested in exploring a romantic relationship, keep an open and honest communication about your expectations," Gottlieb adds.