If someone tried to take the hierarchy thing too seriously - for example, being lovely to producers but moaning to runners about the tea - that would not be accepted on 'Harry Potter'; someone would pull you aside and have a word.

I used to be mad on the games, but I had to ban myself. I used to spend three dollars on games, [but] it adds up, so now I'm on the social side of things like Twitter and Instagram. I love my weather apps. I guess because all the Brits are obsessed with weather.

As soon as you see 'Dame' in front of someone's name, you get nervous, but Dame Maggie Smith is the most wonderfully gentle woman I have ever met. She never had a bad word to say.

I'd rather play a character that was really, really different to me as to someone who is quite close to my character.

I'd like to know about some of the things that they teach down there, like building a lake. If I ever wanted to build a lake, I'd like to know how to do it.

It's remarkable to see the advancements since the early days of [Harry] Potter with putting LEDs on everything, pointing sticks and measuring. Just archaic stuff. Now, it's like one guy with a laptop.

I hope to be scaring children for the rest of my life.