If Harry Potter and the Deathly Hallows: Part 1 felt less frenetic than many fantasy blockbusters, then it was the calm before the storm.

Cast and crew of the hugely successful film franchise have described Deathly Hallows Part 2 -- the eighth and last installment in the boy wizard series due out next July -- as a war movie. And unlike Part 1, it will also be in 3-D.

"In Harry Potter 7 (Deathly Hallows Part 1) ... people keep talking about 'Oh it's an action movie' (but) ... this is so sedate compared to what the next one is going to be like," said British actor Daniel Radcliffe, who plays Harry Potter.

"The next film, because you've had all the plot set up already, you can just kind of enjoy the insanity of all the action," the 21-year-old told Reuters in an interview.

"The last movie is going to be really, really fast paced and a load of action in it and it is like a war film."

Rupert Grint, who plays Harry's best friend Ron, added:

"Some of the scenes where you've got all the hospital beds and piles of bodies everywhere -- it's really a whole new level for a Harry Potter film. It's going to be epic."

Hollywood studio Warner Bros. decided to divide the seventh and last Potter book by author J.K. Rowling into two films.

Part 1, released in cinemas on Friday but screened to critics and journalists already, follows Harry, Ron and Hermione on their mission to find and destroy the Horcruxes -- the keys to evil Lord Voldemort's immortality.

"Chaos" on Set

While there is still plenty of action in Part 1, the actors said they were given more time to explore their characters.

"If we had done this book in one film, the stuff that would have got cut is most of this film," said Radcliffe.

"For me that is the most interesting part of the story, because it's where the characters develop and change.

"My pitch (for Parts 1 and 2) was that it's a road movie that turns into a heist movie that turns into a war film."

But he added that in spite of the "silence and slower pacing" of Deathly Hallows Part 1, it was "the most chaotic to work on by quite a long way.

"It was mad. We all felt the pressure on this film to make it the best, because it's the last.

"Suddenly somebody might wake up one morning and go 'Oh I'm not sure about how my character is in this scene' or the writer would have an idea so we'd be getting re-writes for some scenes the day before they were shot.

"It was constantly moving and had a less settled feel than the other ones had had."

Now that filming is finished, the young actors who grew up on the set of Harry Potter and became A-list stars as well as millionaires as a result, finally have time to reflect.

"It's a really weird feeling," said Grint. "I don't quite know how to react to it. It feels like it's been my whole life and it has kind of taken over my whole life. Now it's finished there's a real sense of freedom.

"I'm excited. It's quite a daunting prospect. We've been in this sort of bubble for the last 10 years and to go out into the real world is really quite scary."

He, Radcliffe and central co-star Emma Watson all said they wanted to continue acting, although Watson is studying at Brown University in the United States and Grint is taking a break.