Like many good love stories, this one begins on a night out. It is spring 2012, and a group of young men sit hunched around a table in Cecconi's, a ritzy Italian restaurant on Melrose Avenue in Los Angeles. They are smart, good-looking ... and on the hunt for women. They bend studiously over their phones, frantically texting girls they know, to see if they will "hang" with them for the evening.
Two metres away is a table of young women on a night out. One of the men clocks them. He has dark, intense eyes and fast, excitable hands. Perhaps, he suggests to his friends, they should try talking to these girls instead. The bolder members of the group approach the women. They then do what young men across the world have been doing for centuries - begin the agonising courtship of small talk.
Sean Rad, the 30-year-old chief executive of the dating app Tinder, laughs when he tells me this story. We meet over lunch in a small, unpretentious cafe off Oxford St in London.
He orders ginger tea and honey, because he tells me, he is "sick". Some sort of cold/flu/temperature thing that he just can't shift.
"I was like ... this is comical! There we were sat in a restaurant all on our phones texting girls to see who would come out. But when I looked around there was a table of girls right next to us!" He takes a sip of tea. On one wrist he wears a chunky silver Rolex. On the other, three "intent" bracelets made of string, the sort of thing students come back with after a gap year. One reads "Dream", the second, "Power". The third one simply says, "Breathe".
"That's when I realised ... sometimes you can't capture what's in front of you. Sometimes you need to make things happen."
Rad describes Tinder as a "social catalyst". In Fast Company magazine this year he went further, in typically forthright language. "The matches made on Tinder can change lives. The Snapchat photo from two hours ago - who gives a f***?" Tinder, he tells me, "makes things that are harder to happen, happen". What that "happen" is, however, is up for debate.
If you're single, under 35 or have children of a consenting age, you will be familiar with what Tinder is and what it does. If you're not, these are the basics. Tinder is essentially a location-based mobile phone app, whose icon - a small red flame - can be found on the phones of single (and sometimes not-so-single) men and women across the world. Users open the app, are presented with an ever-revolving carousel of cheery/pouty/Blue Steel headshots and start swiping. Swipe left to reject and right to give the nod. A conversation is initiated only if both users right-swipe. It's called "a match", the digital equivalent of saying, "I fancy you, you fancy me, let's get this thing moving." Now a whole generation of men and women need never know what it feels like to be rejected.
Some say Tinder has revolutionised the dating scene, facilitating introductions (or, as they're called in Tinderland, "connections") that would not ordinarily happen. Others say it is a "hook-up" app; the scourge of modern love, making empty, one-night sex as easy as, well, swiping right. A Vanity Fair journalist wrote about "the dawn of a dating apocalypse", in which users - men in particular - used it addictively for casual sex.
What happened when they approached the table of girls in 2012? He laughs. "We got rejected! They were like, 'This is awkward. We're eating dinner. Leave us alone!'"
The brush-off did give him an idea. What if you could combine mobile phones and dating, he thought, when he got home. Better still, what if there was a way of knowing whether a woman was interested in you before you made the first move? In the summer of 2012, Rad and a small group of friends got to work. Twenty-three days later, Tinder was born.
Four years on, Tinder facilitates 1.3 million dates a week. There are 9.6 million daily users, accounting for some 1.8 billion swipes a day. Tinder is part of Match Group, which includes other dating sites such as OKCupid and match.com. In November, Match Group was valued at about $US3 billion ($4.1 billion) ahead of flotation on the New York Stock Exchange - according to one recent estimate, US$1 billion would come from Tinder.
If that were all - Rad is reported to own more than 10 per cent of the company - this would be a happy, uncomplicated tale of love, riches and megabytes. But this is start-up land. Things get complicated, quickly. And Tinder's story (by which I really mean Rad's story) has been more tumultuous than most.
"I feel like I have been through more in the past three years than some people do in 20," Rad says with his characteristic lack of guile. He makes an unusual CEO. His forthright, unfiltered manner has polarised anyone who has watched his phenomenal rise, winning him fans - and getting him into trouble.
He says he often gets asked to officiate at Tinder weddings. So far, he has declined.
In 2014, his best friend and fellow Tinder co-founder Justin Mateen had a sexual harassment lawsuit brought against himself and the company by former vice-president of marketing, Whitney Wolfe. Mateen - Rad's best friend - had been in a relationship with Wolfe. When they broke up Rad and Mateen were accused of subjecting Wolfe to "a barrage of sexist, racist and otherwise inappropriate comments".
Eventually they settled out of court for a reported US$1 million, Mateen left the company and Wolfe enacted the sort of coup de grace that could only happen in Silicon Valley: she launched a rival dating app called Bumble - one in which it's the female users who initiate the conversation. Neither side has admitted any wrongdoing, but the case did nothing to resolve Tinder's reputation for having a laddish, jock-dominated working culture. (Like most start-ups, it employs a high percentage of men.)
It got worse. Shortly after, Rad was fired as CEO, with the board citing inexperience. ("It was more about mistakes not yet made than mistakes already made," he says, although observers were quick to note the timing, so soon after the sexual harassment case.) Critics of Rad said he was naive and out of his depth.
Six months later, he was reinstated. Then, on the eve of Match Group's flotation, Rad gave an interview to the London Evening Standard. He said he was "addicted" to Tinder - "Every other week I fall in love with a new girl" - and boasted about a famous supermodel who was "begging" him for sex. This was supposed to be Rad's second chance, but it seemed as though nothing had changed. Was he still a liability? When the journalist asked him what he found attractive he confused the word "sapiosexual" (meaning someone who gets turned on by intelligence) with "sodomy". It went viral.
So let's talk about sodomy, I say as he forks a mouthful of asparagus omelette.
"Oh God," he says shaking his head. "I was really sick, so just bear that in mind." He laughs nervously. "So grasping for the word in my head was partially because my mind was frying." Did his mum read it?
She did, he tells me. He describes her reaction as "confused". So did his team. "But being the laughing stock of the internet for two minutes ... That taught me a lot."
While Tinder has had a lot of growing up to do over the past three years (not least figuring out a way to monetise it), so has Rad. He's 30 now and although he has the boyish enthusiasm of someone 10 years younger, he has the mettle of a survivor.
In interviews in the past he's often described sitting in a bar, swiping through the glamorous women on his Tinder feed as though he can't believe his luck. Today he describes himself as "reserved" and says he finds meeting new people "challenging". He has only had three proper relationships in his life, he tells me, and, yes, he met his last girlfriend, Alexa (daughter of tech billionaire Michael Dell) on Tinder.
"I think the perception is that I'm this LA tech party guy, but the truth is I'd rather sit in a room with my best friends than go to some crazy party." An example: he was recently invited to the Playboy Mansion. He didn't go.
Today, Silicon Valley's heavyweights date like 80s rock stars. Twitter's Jack Dorsey stepped out with supermodel Lily Cole, while Tesla founder Elon Musk married, divorced, married again and then got divorced again from Hollywood actress Talulah Riley. On the week we meet, Rad's friend, the Snapchat founder Evan Spiegel, had just proposed to Victoria's Secret supermodel Miranda Kerr.
It's everything. It's marriage; it's relationships; it's friendships. It's anything that can come out of a connection between two people.
He looks embarrassed when I ask if he is dating. "I am," he says nervously. "But it's early days." All he will tell me is that she is definitely not famous, nor is she a supermodel. The far less glamorous truth is that she works in tech and was a friend before anything happened. "Actually," he concedes, "we're sort of serious."
When he talks about Tinder he rolls at 1000 miles an hour. The anecdotes come fast and furious, the statistics and success stories always on the edge of his tongue. But when it comes to talking about himself he's nervy. Perhaps for good reason.
"Tinder's easy to talk about, right? I know a lot about it. I created it. I've seen it grow. I think in order to talk about something, you need to understand it." There's a pause.
"I think I'm not always good talking about myself, because I'm still learning who I am."
Rad is the son of Iranian-Jewish immigrants.
His parents, who own a successful consumer electronics business set up by Rad's grandfather, live in Bel Air, a smart LA suburb a short drive from Rad's apartment in West Hollywood. Rad grew up listening to the family talk business at the dinner table. He has said, "I got a master's degree in business before I left home."
As a child, his mother, Fariba, was "tough". "Still is," he says, smiling (he speaks to her every day). "Growing up, she'd make me do what she wanted through Jewish guilt. She'd say, 'Oh, you can do whatever you want, Sean, but if you do you'll break my heart!'" He sips his tea. "It's the illusion of freedom."
The Rad family is big - he has 51 cousins, most of whom are in California. Every Friday night extended members of the family meet for dinner at Rad's parents. Rad never misses it. Sometimes he'll go round for dinner on Sunday night, too. He counts two of his cousins as his best friends and his Tinder profile picture is of him with his nephew hoisted on his shoulders.
"This best represents me because I love my nephew and maybe want kids," he says.
As a teenager he was "curious about everything". The family were the first on their block to get an ISDN telephone line and he liked nothing better than to dismantle the router and put it back together again. However, before he got into start-ups, what Rad really wanted to be was a musician. He almost signed with a label, but his parents wouldn't give their permission. Instead, he enrolled at the University of Southern California, only to drop out after two years to start his own tech company, a marketing platform that paired celebrities with brands called Adly.
"My mum was very upset that I left. I'll never forget ... the company I started got a write-up in The Wall Street Journal. It was only like two sentences, but I was so excited that I called home. 'Mum! Dad! You won't believe it. I'm in The Wall Street Journal - it's so cool.' And my mum was like, 'Okay, but when are you going to go back to college?'"
Ironically, this spring Rad was asked back to USC to give the year's commencement speech. Past speakers have included John McCain, Arnold Schwarzenegger and Neil Armstrong. Rad's mother cried throughout. She was spotted, he tells me, running round, stuffing copies of the programme in her bag. "It was one of the best moments of her life," he says.
When he was asked to give the speech, Rad wondered what he would talk about. He was, after all, noticeably younger than past speakers. In the end, he fell upon the most significant moment in his life: the day he was fired.
"I dreamed my whole life of being in a position where I could create something like Tinder and then it was taken away from me," he tells me. "I remember a board member asked me to go for a walk and then asked me, 'So how do you think things are going?' And I was like, 'Really well!' I was sharing all the latest updates and he agreed, but then he said, 'The board feels like we need to bring in a more experienced CEO.' I was like, 'Huh? Where did that come from?'"
After it happened, he called Mateen. "My first question was, am I going to fight this? Am I going to accept this? Because I had a choice. I could have disagreed with the board and fought it. I remember Justin said to me, 'How will you feel if you don't go to Tinder tomorrow? If you don't walk into the office, how will you feel?' And I thought about it and I was like, 'Hmmm ... I would feel like shit. It would feel worse than not being CEO.'"
So Rad stepped down and settled into the position of head of product development (although he was also given the title of president). He knuckled down, tinkered with the product and kept a lower profile. He admits the whole experience "burnt".
"I went through a period where I was like, 'Okay, I don't want to be here anymore. It's not fair. I'm not going to be treated like this.'"
But, by his own admission, he was at the time "out of my depth".
"I never felt good enough. I didn't feel like I was necessarily the most qualified person in the room and that was stressful. I felt immense pressure and responsibility and I didn't feel like I had all the answers. But [being fired] liberated me of two things: it liberated me of the title and it liberated me of trying to be perfect."
A new CEO was brought in, Chris Payne, a veteran tech professional and business leader from eBay. He lasted less than five months before Rad was reinstated. (There was a standing ovation when he walked back in as CEO.) Why Payne didn't last longer, no one appears to know. But when you enter Tinder HQ, the Frank Gehry-designed glass building on Sunset Boulevard, you get a sense of what might have happened (outside, Tinder tourists pose for selfies beside the logo). Tinder is a young place. There are beanbags and people hunched over laptops in high-top trainers and low-rise denim. There is a wall of candies, a basketball court, a fancy-looking drinks area that dispenses three different types of kombucha, the fermented tea, as well as wine and beer on tap (otherwise known as "the winerator" and "beererator"). You get the feeling anyone who remembers plaid shirts and Dr Martens the first time around might have a tricky time fitting in.
While I was there I met a pretty, bird-like young woman called Jessica Carbino. She has the job title of Tinder in-house sociologist. I was eager to meet her because, I was informed, she "matched" with Rad on Tinder. That's kind of embarrassing, I say, to be working for the guy you right-swiped.
She tells me that Rad made it "very clear" early on that his was a professionally curious right swipe. "He was like, 'Hi Jess, what are you writing your dissertation on?' I had on my profile that I was a PhD student in sociology, so he was very curious about that. It was nothing but professional from the get-go."
If she's disappointed she doesn't let on. Instead she tells me she met her current partner on Tinder. Actually, a quick, highly unscientific canvas of the office reveals many of the Tinder team have. too. She is very keen to press this last point on me. "Eighty per cent of our users are looking for a relationship that's not casual in nature," she says.
Ah, yes ... sex. The only time I have seen Rad look mildly irritated is when Tinder is referred to as a "hook-up" app. Rad seems to spend a good proportion of his time convincing people that Tinder is about more than a right-swiped shag.
"We have made over 20 billion connections," he tells me almost wearily.
"I think people would hook up regardless of Tinder. People will use Instagram; they will use any app. It's a fallacy to think that's all that's happening. To assume that all 20 billion of those connections are one-night things is wrong. It's everything. It's marriage; it's relationships; it's friendships. It's anything that can come out of a connection between two people."
At work his focus isn't just on improving Tinder's core functionality - it's on how to broaden the app's appeal and generate revenues that match its astonishing cultural significance. Currently no other app is as successful at helping strangers meet and it's easy to think of ways that Tinder could build on the success of businesses like LinkedIn. (As Rad pointed out in Fast Company, "LinkedIn sucks for meeting new people.")
Last year, Tinder introduced SuperLike, which enables users to alert people that they have liked them. SuperLike is included as part of Tinder Plus, the company's premium subscription service. The basic app is free but for a monthly fee Tinder Plus gives members unlimited swipes and five SuperLikes a day. Rates are more for the over-30s (as Rad said, with typical bullishness, around the launch to one interviewer: "How much would you pay me to meet your future wife? Ten thousand dollars? Twenty thousand dollars?") The latest innovation is a new platform called Tinder Social. Essentially, it allows you to plan your night out by inviting people you know, as well as matching with other groups who are going out that night, too.
He could have done with that on his night out in Cecconi's, I say.
"Right," he agrees. "It's come full circle."