“For a start, there’s Felix Felicis, which is a drug that gives you perfect luck. You take it and everything goes right for you, but it also heightens your senses somewhat and you get quite 'breezy’ with it. Then there’s a love potion that makes you very tactile with everybody.”

Harry (played by Daniel Radcliffe) finds himself drawn to Ginny (Bonnie Wright), while Lavender Brown (Jessie Cave) has decided that Ron (Rupert Grint) is the one for her. And then, of course, there’s Hermione (Emma Watson), simmering with jealousy ” Ron should be hers” but determined to keep her true feelings hidden.

“There are some really lovely comic beats in there,” continues the 46-year-old British filmmaker. “With the love potion, for example, Rupert at one point gets overly tactile with Jim Broadbent’s [newly introduced] character, Professor Slughorn, which is hilarious. We didn’t really get a chance to bring those moments in last time round.”

“It’s funny how things change,” he offers. “I felt really self-conscious making this last film. The first time, I didn’t realise how big it was until I got to the premiere and then got to America and saw how massive the release was, and how huge the reaction was. That was when the penny dropped, when I realised that this was such a big thing for so many people.

“Oddly, that meant that when I started this one, I was a little bit warier of everything rather than being more confident. The first time round you just do it; you just go for it. But I have settled in and this one’s quite different from the last one. It’s a little bit more grown up and a bit wittier. It’s a different vibe.”

“I remember when Jurassic Park came out and that was quite a violent movie, with all these cutting-edge special effects,” Yates says. “But because it was Steven Spielberg, people said, 'We think kids will go with it.’ “And I think that’s true here: because it’s Harry Potter and because of the fanbase, I think there’s a higher tolerance for what we can present to the audience. The viewers know the world and they’ve read about these things and they’ve experienced it on the page. Hence we are able to do a little bit more than maybe other films can.” He smiles. “That’s the beauty of Harry Potter.”