Devin sees the Battle of Hogwarts for himself.

Hogwarts is in ruins. The castle walls are pocked with blast holes, and there are fires crackling out from within. The common square is filled with rubble. Just outside the main entrance Madam Professor Minerva McGonagall stands on the steps with a cadre of students, wands at the ready, prepared to fend off the Death Eater assault on the wizarding school. And then, from within the castle itself, marches a dozen suits of armor, magically brought to life to aid in the final battle.

That’s how you’ll see it in the movies, at least, when Harry Potter and the Deathly Hallows Part II opens. When I was there last year the castle was just a facade, and much of the damage was in the form of blue screens attached to the front. The students and McGonagall were all there, but the suits of armor were just stunt men in grey sweat suits. It was a bitterly cold night and the exhaustion from the cast and crew was palpable; this wasn’t just the winding down of the last Harry Potter movie, this was the winding down of over a decade of work.

But making movies isn’t like watching movies. The Battle of Hogwarts, while one of the later things being shot for the film, certainly wasn’t the last thing being shot. Since movies aren’t shot in sequence the finality of the narrative isn’t reflected in the shooting schedule.

“You do things in the wrong order always,” explained Stuart Craig, who has been production designer on the series since the first film. “So it isn’t as final as you may believe it is. In other words, you don’t build a nice, pristine set, shoot it in good condition, and then ruin it and it’s gone forever. It’s not like that. For some reason, in movie schedules, you always end up building it ruined first because it’s harder, and then you make it good again.

“And that’s exactly what we’ve done, in fact. We are building it ruined, and then making it good, and then making it ruined again, and it’s all to do with actors’ availability.”

There are some aspects of the world of Harry Potter that never come down, though. The Great Hall, where the students take their meals and meet at the beginning of every school year, has been standing for years and years, once it became clear that they were going to keep needing the set in movie after movie. Albus Dumbledore’s office also has stood for years, through the deaths of actors and characters alike. The books that line his walls are actually redressed local phone books, the only magic being the numbers of residents in the immediate area of Leavesden Studios.

And while the Harry Potter films are ending, the sets will remain. You’ll be able to take a three hour walking tour of them - as well as see many of the costumes, props and beasts that remain stashed away all over Leavesden - in 2012. I’m not sure the last film where that happened, where the sets became a permanent exhibition; DW Griffiths’ Intolerance left its massive set in the middle of Los Angeles for decades, but that was taken down long, long ago (although the newish Hollywood and Highland complex, where they hold the Oscars, is designed in the style of the Intolerance set). The series is leaving its mark - culturally, physically and especially in the lives of the actors who starred in all eight films.

Like Matt Lewis. When he first signed on to play Neville Longbottom when he was 9 or 10 years old he couldn’t have imagined where the films would take him. For one thing, Neville’s character was very different in those early days, and JK Rowling hadn’t even written the books where he would change from a chubby dork into a hero who… well, I don’t want to spoil it if you haven’t read the books, but Neville has some pretty badass moments in Deathly Hallows Part II.

Lewis found out about Neville’s heroism before the rest of us, if in vague terms. “I remember when I read number five; I was just going back to school after half term and I read it. I went to the bus stop in the morning and asked my best mate Anthony if he’d finished reading it and he said, ‘Yeah.’ He was like, ‘You’re going to have some wicked stuff to do.’ That’s the first time I found out was when I finished number five. The battle stuff we did there was cool. I really enjoyed that. I had no idea what he’d go on to do in number seven. The only idea I got was when I spoke to J.K. Rowling at the premiere of number five and she said to me, ‘I’ve written some really cool stuff for you for number seven,’ and I was like, ‘Don’t tell me anything. I don’t want to know,’ and she said, ‘Okay, but you’ll enjoy it.’ Then I read the book and I was like where is it? She promised me and then it comes at the end of it. It was pretty cool. So I’ve spent the last couple of years waiting for this moment. It’s really fun.”

Since I don’t want to spoil it for you, I’ll let Lewis explain some of what coolness Neville gets. “Neville this year is sort of taking over Harry’s role,” he said during an on-set interview. “He’s the unofficial leader of Dumbledore’s Army. He’s sort of barking out orders to people and telling them where to go. He’s really evolved into this leader which I never thought years ago he’d end up doing. It’s really cool to see and to play.

“I think he’s watched Harry all these years be a leader and have so much courage. As he’s seen Harry take on all these responsibilities from everyone, he realizes that they’re not too dissimilar. They both lost parents at when they were very young. He starts to think that maybe he can do this and when Harry leaves the school in number seven, Neville realizes it’s his time to step in and take responsibility. He’s always had this good heart. He always wants to do the right thing and look after people, but he’s never really had the courage to do it and now he’s thought, ‘Okay it’s now or never. We’ve got to fight this evil. If no one else is going to step up then I’ll do it.’ That’s what he does and he’s not perfect, but he gives it a go.

“Every year we’ve tried to focus very much on that part of Neville—this idea that he’s so much more than just the geeky one that fell over and stuff. There was always an underlying thing there and slowly as the years came on we tried to add a bit more to his background. I think this year we really show Neville coming full circle. He’s now this leader that Harry was before he left. It’s pretty cool and I’m really looking forward to it.”

That leadership quality comes to the fore in Deathly Hallows Part II, a movie that’s essentially one long climax. “The second film essentially is the final battle, I mean, from start to finish,” Daniel Radcliffe said on set. While he wasn’t working the day that we visited Hogwarts, the actor came in just for an interview. “The action sequences are pretty relentless in the second part, you know, it’s very, it’s nonstop kind of action to a degree.”

Director David Yates agrees. “I love the notion of parachuting straight in. I love the notion that the audience has experience six or seven of these movies and they don’t need an intro. They don’t need a big bang so the notion where you parachute in from the first minute I think is really fun. Steve [Kloves] wrote a first draft of the second part with that spirit. When I first read it I said, “Steve this is great. It doesn’t have a beginning. It just goes.” You’re in it and you’re just off. I really like that. So that’s kind of the spirit of how we’re approaching Part II.”

Outside in the cold night Dame Maggie Smith, the real life Muggle behind Minerva McGonagall, blows a line. She swears at herself, and somehow her aristocratic accent makes the curse word dirtier and funnier. Devon Murray, who plays the mischevious Seamus Finnigan, laughs. They’re going to be out here for a few more hours. And then there’s still weeks to go. And beyond that there’s the post-production, with looping and reshoots and all that. Finally comes the press for the film. And then, last of all, the premiere, which happened last night in London. As of this writing, they’re finally done with Harry Potter - unless Warner Bros decides to call Radcliffe et al in for a commentary track on the Harry Potter 20th anniversary Blu-ray rerelease.

A year ago on set Radcliffe gave the right answers when it came to the sadness of parting with the cast and crew: “I’ll miss the crew and the sense of family that we have here is something that it will be very hard to recreate on other films. I think it’s possible, I don’t think it’s that I’ll never be on a set this close again, but there’s people here who I have, as you say, I’ve known for ten years and I’m very, very close to, so it will be a sad day.” But talking to him that day he felt a lot like a high school senior, vaguely aware that he was going to miss these days but ready for what comes next. “It’ll be exciting to go onto other things and see what’s out there and that’ll be great.”

Somebody asked Radcliffe if there was a prop or costume he was going to keep. His answer: the glasses. In real life Radcliffe doesn’t wear glasses, and it’s almost weirdly disorienting talking to Harry Potter without those frames. “I’d really like the glasses, and hopefully the lenseless ones because they’re the ones I wore most. So, I’d like them more than the proper ones. Even the wand is not such a big deal to me because the wand was different in the first two films. So even that hasn’t been a constant through all seven. The glasses would definitely be the keepsake for me I think.” He thought about it for a second. “I found my script from the first film the other day, all highlighted up, yeah. it was good.”

Click here to read my report for Harry Potter and the Deathly Hallows Part I