The queue of models and hipsters snakes outside the Shoreditch House club, demanding access to the exclusive rooftop event. The star of the show meanwhile is keeping everyone waiting in her dressing room.
Finally E L James sweeps into the room for a rare speaking appearance which marks the 50 Shades Of Grey author's formal elevation from self-published fan writer to literature's Lady Gaga. Listed in Time magazine's 100 Most Influential Women, the first-time writer whose erotic fantasy novels have become a 40-million-selling phenomenon, is adapting fast to diva-dom.
Ms James, 48, agreed to a brief on-stage interview, held at the East London members' club, to launch the latest brand extension endorsed by the mother-of-two from West London.
50 Shades Of Grey: The Classical Album, released by EMI, features 15 pieces of music referenced during the steamy, S&M-tinged encounters between student Anastasia and billionaire Christian Grey.
Such is Ms James' influence that a mere mention in the first novel of Spem in Alium, a 16th century motet for 40 voices by Thomas Tallis, sent the download to the top of the classical charts.
Mark Ellen, the music journalist who has interviewed megastars from Michael Jackson down, was selected to conduct the conversation in front of an invited audience, secured in risque handcuffs after gaining entry.
Ellen informs the audience that James will speak for only 15 minutes and will not take questions or sign books, restrictions no less rigorous than those imposed by the King of Pop's handlers.
When James, whisked through the throng by a retinue of handlers, takes the stage, she parcels out insights into the extraordinary sequence of events which has seen the former television executive earn an estimated £20m inside 18 months.
"I thought I'd continue working and writing in the evening like I was doing. But it's just taken off and I still don't quite believe it," the woman at the centre of the whirlwind says.
A mid-life crisis spawned the best-selling book in Britain of all time. "I worked for a company and I was incredibly miserable. Then I discovered fan fiction after reading Twilight. I started writing. It was good. I stopped going out and getting drunk so much."
When 50 Shades was released as an e-book last year, Ms James was taken aback by the demand. "It was never my intention to publish; I really did it for myself. Then a friend of mine had his book published and I thought 'if you can do it, I can have a go'. So I did and here I am."
Yet Ms James is also a smart marketer who ensured that her target female audience could indulge in 50 Shades' bondage fantasies without public embarrassment. "I designed the book covers," she said. "I used to read a lot of romantic fiction on the tube and they had these horrible covers of women with their clothes falling off. So I designed really discreet covers for the books so no one would ever know this was a very salacious novel."
It's sex though, the kinkier the better, that the audience, which includes the actress Jaime Winstone and refugees from the cast of Made In Chelsea, really wants to hear about.
What songs lubricate James's juices? "I had a lot of fun researching these books. Music to f*** to. We all want that. I have songs I write sex to. The Black Eyed Peas' 'Sexy' is a very sexy song."
Defending her books as "passionate love stories" – against claims of "mummy porn" – the writer argues that they have changed lives for the better. "People of all ages are reading it, from girls at university to women in their 90s. Those emails are an interesting read.
"The emails range from people saying 'you've saved my marriage' to 'thank you, the Siberian child we adopted who couldn't be touched is having therapy and now getting married'."
After selling the film rights for $5m to Universal, James is staying out of the debate over who should play her protagonists. Ryan Gosling and Scarlett Johansson have been touted, but she says: "That's not a road I want to travel. It's best to keep your mouth shut."
Her future literary ambitions remain unclear although she may submit to reader requests to write a follow-up entirely from Christian's point of view.
Like Lady Gaga, she is about to embark on an international tour. Visiting Portland and Seattle will give her a chance to visit the books' locations. "I've never been," she admitted. "I researched everything on Google Street View."
What does she intend to do with the huge influence ascribed to her by Time? "It's overwhelming. I try not to think about it too much. I wrote these books for myself. Other people seem to share my fantasies too. It's a huge relief to find that I'm not alone."
As flashbulbs pop, the author herself is bundled straight out of the bar to a private room where she is lavished with Venetian cake, leaving an audience of Shoreditch's finest desperately seeking a key to unlock their handcuffs.
'Sex sells, but you stay for the love': What fans say
Cookie Rabiu, 18, Camden
I was the first here at 7am. I'm a die-hard fan. I've read them all three times but I've bought new copies today for her to sign. I wouldn't mind a man who looked like Christian Grey, but I wouldn't want all the freakishness.
Amanda West, 28, Reading
I'm going to tell her she's made my life more interesting. It has clicked with a lot of women because although we used to think about the kinds of things that were in the books, we didn't talk about it.
Anthony Strutt, 50, Leicester
I got on a coach at 5am to be here. The books are definitely written for women, and the first one is quite badly written, but I loved the stories. My girlfriend hasn't read it, in fact I think she's deliberately avoided them.
Joy Ashworth, 21, Coventry
I run a Facebook page about the books and I've written an essay about them to give to EL James today. They helped my relationship, and really held me and my partner together – it really spiced things up. Sex is what sells it, but you stay for the love.