Harry Melling is over Harry Potter. “I kind of want to let it go,” he says. “It’s done.” The 27-year-old spent his teenage years playing Dudley Dursley, Harry’s brattish cousin, in what would become the biggest British film franchise ever. It’s not something that’s easily shaken off. “I don’t know if it will ever really be done. People will still go, ‘Oh you’re Dudley Dursley, the fat one’.”
In many ways, he’s not. Not any more. He still attends the odd convention – “very difficult,” apparently – but out of context, Melling is unrecognisable as the tubby muggle. He was 10 when he won the role and, at 18, on the cusp of drama school, he decided to lose weight. “Not because I wanted to play skinny parts, not even to be healthy, just to lose weight,” he says. “I started running the next morning. I didn’t know why, but I now realise that it was about not allowing people to pin you down.”
For the final two films, he had to play Dudley in a fat suit. The role was nearly recast. He had put a distance between himself and his part. In fact, he felt he had to.
Reinvention has become a big part of Melling’s practice. He’s grown into one of the stage’s great shapeshifters: here stuttering his way through Mother Courage at the National as the damaged Swiss Cheese; there swaggering around Women Beware Women in plus fours and Pringle socks as the effete Young Ward. One moment he’s meek, as in Jamie Lloyd’s The Hothouse; the next boyish and upbeat as Lear’s Fool for Chichester. He’s got a good face for it: handsome, but doughy, it suits both simple-mindedness and smartness, the browbeaten and the bullying.
His latest reinvention involves turning playwright. Melling’s debut play Peddling, a whiz-bang of a monologue, premiered at the HighTide Festival last year and, after a stint in New York, reopens at the Arcola this week. “People think they know what you are and what you do,” he says. “The thing that I want to do is battle against that, not allowing people that security.”
That attitude, though, goes back to Harry Potter – in more ways than one. When he started out, of course, Harry Potter wasn’t the cultural icon or the cultural industry it is today. This was before the midnight releases, the adult covers and, obviously, the star-stuffed films that have so solidified the books’ status. Two books had come out to positive reviews – Melling had read the first – and we knew five more would follow.
Did he grasp the enormity of what he was stepping into? “No, not at all,” Melling replies. “Once the first film was out, people started to realise exactly what a franchise this was going to be. That was when the films started to change. They took on a formula.”
For him, it mostly meant one month a year mucking about in a suburban semi with Fiona Shaw and Richard Griffiths. He watched both actors intently. “Their way of working was very simple: it’s all about finding a game. Both of them had a huge spirit of fun.”
Melling’s caught it – or maybe he cultivated it. Either way, he’s puckish onstage, always out for a bold choice and a big character. He’s the sort of actor that plays in public; one that takes risks and puts himself out there. That comes, too, from a long stint in the National Youth Theatre, which he joined at 13, working alongside Matt Smith and Shane Zaza.
“Harry Potter gives you a sense of needing to prove yourself beyond the whole child actor thing,” he explains. “It’s a great opportunity, a great platform, but how do you go on from that?”
Melling doesn’t think he’s the only one feeling that: “Dan [Radcliffe], in terms of his choices, going into theatre and independent films, I think he feels that too. He’s not going to do The Hunger Games, he’s trying to prove himself. They all have, actually; all the ones that wanted to do it.”
His first step was drama school. LAMDA, to be precise. “I knew that I needed it. There were things I wanted to sort out.” Mostly, he “just wanted to get a process”. While there, he had a lightning bolt moment, playing King John.
“I think there’s always one role you play at drama school when suddenly everything clicks into place… I worked really hard on it and then, two days before the shows, I just forgot all the work. I got onstage without worrying about all the work I’d done, without trying to remember stuff, and I just did it.”
That’s harder to do with your own play, perhaps, especially when it’s had several incarnations over the years. In Peddling, Melling plays a waifish teenage boy who goes door-to-door, selling bits and pieces. It’s a fizzing piece, somersaulting with raggedy street poetry.
The character comes from life. “I met this boy when I was eight,” he says. “He came round our house, selling Marigolds and things. My dad opened the door and said, ‘Nothing today,’ so he went away very politely. Then he just flipped – lost it – and started throwing stones at the house, swearing. I was eight, in my mum’s bedroom looking down at him. That stayed with me.”
Years later, at 24, he started again, on a whim, in the Bush Theatre cafe. “There came a point where it was so bad that I had to make it good. I just wouldn’t stop until it was good.”
How has Melling managed the two roles, of actor and writer? “I didn’t write it for myself. I just wanted to write it.”
A friend suggested he take the role himself. “That changed my writing. Before it was very Philip Ridleyesque and I realised that wasn’t me, but a version of someone else.”
Working with HighTide, putting the play through a couple of readings, he started to found his voice.
However, when it came to staging Peddling with HighTide’s artistic director Steven Atkinson, he tried to keep some distance between his two selves. “In rehearsals, I was just acting as if the script was someone else’s.” If he let the writer into the room, he says, perfectionism set in. Rewrites were confined to the evening.
Melling’s on to his second play – or, at least, it’s brewing.
“It’s about a theatre critic who falls in love with a theatre usher,” he says.
“It’s out to question why we bother; why we go to the theatre at all. Is it because someone says it’s good or are we holding out for the five-star review?”
What is theatre for Melling? “I think the act of theatre can save people. Without sounding too” – he tails off – “People offer something of themselves for a group of other people. That’s something we should do more of. When theatre’s good, there’s nothing like it. Nothing comes close.”
Peddling runs at the Arcola Theatre, London  until March 28