'I can grow a good 'tache'

IT'S quite something, walking in on Rafe Spall draped over a sofa reading a copy of The Lady, chuckling to himself. In a rumpled white shirt, with scuffed up hair, the somewhat burly Life Of Pi and One Day actor manages to just about drag his eyes away from the magazine before blurting happily: "Sorry! I'm going to engage with you thoroughly!"

Charming, affable and properly delightful company, Spall is appearing in the latest big-screen adaptation of Arthur Ransome's adored children's book, Swallows And Amazons.

Not that he'd read the book before filming started, but, he explains, he'd always been aware of it being "part of a cultural fabric of this country", and how could he not?

It tells the exploits of the Walker children - an adventurous brood on their holidays in the Lake District, who persuade their mum (Boardwalk Empire's Kelly Macdonald) to let them camp out, sail about on a borrowed boat called 'Swallow' and battle the two Blackett sisters for ownership of Wild Cat Island.

Spall plays Captain Flint - allegedly based on Ransome himself - a mysterious, moody figure who attracts the attentions of the children, as well as a secret agent (Sherlock's Andrew Scott).

Director Philippa Lowthorpe sold him on the part of Flint by promising a "dashing Robert Donat, 1930s film star character", and the final cut isn't far off.

"I thought, 'Well, I'll grow a moustache, I'll get real nice quiffy hair and I'll put on some nice suits and it'll be really fun'," Spall says jovially, adding: "All I want to do now is read scripts if I think I have something to offer them, and if I think they are a force for good in the world, then I'll do them."

The moustache is a success in itself.

"I have to give myself some credit that I can grow a good 'tache pretty quickly; that wasn't always the case," he admits, remembering how, when he starred in Simon Pegg's comedy Hot Fuzz, aged 24, he and co-star Paddy Considine were both told to grow one. "We came in the next day, Paddy had a full moustache and I had to paint mine on with mascara!"

Now 33, Spall is both hirsute and a father. He and his wife, former Hollyoaks actress Elize du Toit, have three young children together, and he says that starring in Swallows And Amazons has really made him consider the difference in freedom kids have today, compared to their 1930s counterparts.

"It's pretty crazy. That mum lets those kids go off to cross the deepest body of water in the UK, and can't even say, 'Text me when you get there'," he muses. "It's a reminder in this age of information, when people are glued to their devices, that we have this extraordinary countryside, this amazing world, and that it should be seen as an encouragement for children to go out, get muddy, get dirty, look after each other and themselves, and have adventures that don't involve a computer screen."

So, would he let his own kids camp out?

"No," Spall barks without a second's hesitation. "I'd let them camp out in the garden! I live in London, where are they gonna go? Hampstead Heath? That's not a place you want children at night!

"Who knows," he continues, "when they're old enough, whether I'll trust my eldest daughter to look after the rest of them? I just want them to want to do it, even though I could say no."

Spall, whose career started at the National Youth Theatre after he failed to get into drama school, wasn't massively adventurous as a child himself ("I watched a lot of telly"), although, much like the Walker children, he did grow up understanding what it's like to be on the water, thanks to his parents' canal boats.

"But when you get to 15, it's the last place you want to be," he says with a laugh, "in a confined space with your mum and dad. So I gave that up."

Of course, 'dad' here, is bona fide national treasure, the great Timothy Spall of Harry Potter and Mr Turner fame.

"Any association there is between my dad and me, I'm nothing but proud of, and delighted by," says Spall of the link always being drawn between the two. "It's cool, because I'm very proud of him, and to be associated with someone that you love and respect so much is just great."

He pauses, then splutters: "It's not like he's on TOWIE!"

Spall says his own kids are very "unimpressed" watching him on screen.

"I did a Christmas film called Get Santa where I'm prison. [They said] 'You're in prison? What did you do?'

"I said, 'It's not real!'

"'You met Santa Claus?'

"'Yes, I did meet Santa Claus'.

"'So you were in prison too?'

"'No. Shut up. Go to bed!' It's pretty confusing for the little'uns," he adds with a laugh.

More recently, Spall's popped up in The BFG ("It was really fun, doing scenes, and then you look over at the monitor and there's Steven Spielberg, who looks exactly like the image you have in your mind"), and The Big Short alongside Hollywood heavyweights Steve Carrell, Ryan Gosling and Brad Pitt, which he admits was mildly intimidating.

"On your first day, you can't be like, 'Oh my God - look who it is! LOOK! Ohh, how weird!'" he says with a grin. "You're trying to be really cool. But if I get really nervous, I get really slouchy and relaxed, so when I first met Brad Pitt, I was like, 'Hey man, so nice to meet you' [he gets up and pretends to slide down a wall]. It's like, what are you doing?! Stand up straight!"

Next up, Spall will be appearing in a horror film, despite being a self-confessed scaredy-cat and, he jokes: "I'm going to be in Geordie Shore. I'm going to be one of the regulars on that, which is pretty exciting."

And then I'm A Celeb afterwards?

"Fingers crossed!"

• Swallows And Amazons is in cinemas now