J.K. Rowling: It’s really weird you’re asking me that question, because four days ago I wrote the answer in the fourth Robert Galbraith book. Because when you meet my detective in book four, he is reflecting on how success never feels the way you think it will be.

Some people would assume that you’re sitting around feeling simply marvellous and shining your baubles. But I remember, a week after I got my American deal, which got me a lot of press, one of my very best girlfriends rang me and said, “I thought you’d sound so elated.” From the outside, I’m sure everything looked amazing. But in my flat, where I was still a single mum and I didn’t know who to call to do my hair, everything felt phenomenally overwhelming.

For the first time in my life I could buy a house, which meant security for my daughter and me, but I now felt: “The next book can’t possibly live up to this.” So I managed to turn this amazing triumph into tragedy, in the space of about five days.

Rowling: I always knew Warner Bros wanted to do something with Fantastic Beasts and, being slightly control-freaky, I thought I’d better tell them that I had an idea. Then I sort of wrote a screenplay without meaning to. I know that sounds incredibly disingenuous.

Rowling: Big Smiths fan. And the people who mean something to you at 16, 17 are the people who are getting you through stuff. So I absolutely understand why someone who is hanging on to Harry Potter as a safe place at 13 is excited at 21 to talk about what [Hogwarts] house they’d be in. I don’t think it’s infantile.

I don’t think it’s any more infantile than me being excited to meet Morrissey. I was with my sister-in-law and she said, “Put. Your. Hand. Down.” I was walking around afterwards with my hand out like that [mimes a stiff handshake].

Lauren Laverne: Like a Dalek.
Rowling: I said, “Morrissey touched me!” She said, “I know, you look stupid.” I met him in such a bizarre situation, in Harvey Nichols. We were looking at each other, getting nearer and nearer, and at almost exactly the same moment we both put out our hands. What was amazing to me was, Morrissey knew who I was.

I wanted to go back to my 16-year-old self, who’s lying there in the dark with the joss sticks, listening to Heaven Knows I’m Miserable Now, and tell her: “You’ll meet him! He’ll know who you are!”

Lauren Laverne: But Twitter for you is obviously very comfortable.
Rowling: You’re swimming in your own medium. Twitter for me has been an unmixed blessing, trolls included. Because there came a point where Harry became so enormous that, at a reading, there were 2,000 people. You can’t answer everyone’s question. Twitter gave that back to me. No one has to buy a ticket. It’s very democratic.

Rowling: My block and mute lists aren’t long because I have quite a high tolerance for people I wouldn’t necessarily want to be friends with – I’m interested in what they’re saying. You wouldn’t want to sanitise your timeline to the point that you weren’t seeing some of these characters. Let’s call them characters. When did you start tweeting?