MARTIN

"Can I explain why I want to kill myself? Of course I can. I'm not an idiot."

"Martin was a tough role to cast and we're delighted that it ended up being Pierce," says Amanda Posey. "He's got exactly the right mix of comedic and dramatic chops that the part required."

Not that the actor has experienced anything similar in his own life to what Martin endures, but Brosnan brings believable A-list baggage to the role of a man who has watched his fame evaporate in an ugly scandal. While some actors shied away from Martin because of the character's sexual indiscretion with an underage girl, or the fact that they simply didn't want to play a character who begins the film as such a failure, Brosnan had no such concerns.

The fifth actor to portray British super-spy James Bond in that enduring franchise, Brosnan has spent his post-007 career diversifying, seeking out distinctive and confronting parts for himself. There was nothing daunting for Brosnan in portraying a character as acutely flawed as Martin Sharp. "The story has such a humanity and charm to it," he declares. "It's poignant, it's caustic, it's acerbic and it moves around the stage with a nimble flair."

"It needed a brave actor who was comfortable in his own skin," adds Dwyer. "Pierce is at that stage in his career where he can do what he wants to do, which is exciting for him and for us."

Apart from Thorne's script, Brosnan was lured by the prospect of working with Chaumeil, having admired his 2010 film Heartbreaker. "Pascal came out to my place and we had a lovely lunch and he was so well versed in the world of Nick Hornby… I thought, 'Let's do it,'" says Brosnan, who also had lunch with Hornby before accepting the role and thus had the experience of hearing both men praising each other's passion for the story.

Brosnan liked the cast that was being assembled, too. "I've admired Toni Collette for many years – she's such a chameleon; I knew and loved Imogen Poots' work; and I checked out what Aaron Paul was doing on Breaking Bad and was bedazzled by him. All the ingredients made sense."

Brosnan's role is a delicate one in that Martin Sharp, in the eyes of the British courts, is a paedophile. "He's a TV presenter who wasn't very good at his job and who had sex with an underage girl," says the actor. "She looked 25, but how was he to know?" Having done his time and watched his talk-show career vanish in scandal, Martin is sad, miserable, alone, but also possessed of a natural wit and charm that make him a likeable guy. For Brosnan, it was about finding a way into into Martin's emotional regret and devastation that would made the character tick.

"I loved playing him," says the Irish actor. "He's adrift in life; he wakes up every morning and feels humiliated. He's got an ex-wife and two children, which compounds the tragedy of his life because he's estranged from his daughters. And he just wants to be famous again, which is a sad state of affairs for a fellow who should know better. At the end of this particular year, he wants to go to the top of Topper's Tower and throw himself off."

Even though Martin's TV career has already come to a crashing halt by the time A Long Way Down commences, Brosnan still studied a few talk-show hosts to garner tips and nuances, including one very famous former breakfast TV host: "Richard [Madeley], from Richard & Judy, came to mind," he says. "I know them and they're delightful people. I was sitting in La Colombe d'Or of all places, the restaurant near Nice, while I was shooting a film in France, and I was thinking of Richard and had been watching him. The next thing, I look up and there was Judy sitting opposite me! I thought that was quite serendipitous. And, by the way, Martin is nowhere near as good as Richard or any of the people I watched."

Brosnan can also fully empathise with the intense media scrutiny that A Long Way Down's surrogate family endure. "Being documented by paparazzi is an affliction of our business," the actor notes. "I live a fairly normal life as a man and as an actor; I try not to bump into the furniture, so to speak."

On set, Brosnan admired Chaumeil's flair for composition, as well as his quick and informed decision-making. "He's very specific and he has a wonderful ear for the comedy," says Brosnan. "He keeps it simple and he keeps it moving. A film like this that shoots for eight weeks can be just as intense, if not more so, than your three or six-month shoot. Time is precious so you hope and wish for a crack unit, and we do have that, from our DoP to sound to costume to our seasoned producers, Finola and Amanda."

The strong bond that's formed between the film's four stars is a key reason for their chemistry up on screen. "From day one, we've been kind of joined at the hip," says Brosnan. "It's always invigorating to work with talent as good as that. It keep you on your toes. There's just been a lovely unity to us. We have each other's backs in the scenes, so to speak, which is less common than you might think."

Chaumeil came away very impressed by the star. "For an actor as experienced as he is," says the director, "you can tell Pierce still really wants to give his best. He brought a lot of depth to Martin, and maybe a bit more pain than there was in the script."

"Pierce is quite a shy man, actually," he continues. "He has a strong personality and the qualities of being a leader because of what he's done, but I don't think he wants to be a leader. If there was a leader of the gang, it was Toni. At least she was the one organising their trips to restaurants and things."

JESS

"I'd never kill myself with pills. Jumping off a tower block is way, way cooler."

Invited to join the cast after Brosnan and Collette were on board, Poots was immediately drawn to Jess as a complex and well-written character. "She's a dream part for sure," says the actress, who has swiftly risen to prominence in recent years with her roles in 28 Weeks Later, Jane Eyre and The Look Of Love. "She's so rich and such a wonderful character to play. She's the instigator for calling off the suicides that night. She essentially forms this unusual family unit even though she's the prickliest and, at first sight, least accessible character. I think Jack Thorne's done a great job of adapting her from the novel to the screen."

The actress bonded instantly with her co-stars, and jokes that the foursome became "socially inept with anyone else while we were making the film… You grow to love people when you're in such close proximity and you have the beauty of comfort, and they're all good people with dirty, brilliant senses of humour," she grins. "Pierce just makes me laugh – he's so funny. Toni I knew each other from a film we did together called Fright Night and it's been wonderful spending time together; I love her. And Aaron is the most gentle, thoughtful human being. It's just a joy to work with all of them."

She is equally magnanimous in praise of her director, complimenting Chaumeil's generosity and unwavering support on set and citing her deep trust and respect for him. "He's always right because he's so clever," she says. "And even though he's French, he has this wonderful understanding of British humour, the sarcasm and dry wit that comes with all of that and that plays out in the script."

Poots also relished Jess's thrift-shop look, and embraced the challenge of the many emotional scenes she got to perform as her tormented character. "She's someone who goes from intense upset to a kind of frantic glee," says the actress. "There are elements to Jess that are fundamentally irritating but it is important to me that they don't put people off her because beneath all the frantic energy and the sarky comments, there is somebody who just wants to learn how to be accepted."

"Imogen is a gift," declares Chaumeil, "and she's fantastic in the film. I don't think Jess in the book or the script is as vulnerable as Imogen made her. She was more of a bad girl, but Imogen brought something so fragile to the role as well as being really, really funny."

JJ

"I'm bored of being scared all the time and not knowing why."

"JJ is a lost kid just struggling to find purpose in life," says Aaron Paul. "He's constantly trying to find new ways of being happy, but he's struggling to do that, and that's why you meet him on that rooftop." In A Long Way Down, JJ is a failed American musician living in London, whose rock-star dreams have fizzled out and who's ended up delivering pizzas to make ends meet. Hornby's novel spells out that JJ arrived in the UK chasing after a girl, and ended up in heartbreak hotel as well as his own emotional dead-end.

"He's in a dark place when we meet him," says Paul. "He's tired of being scared all the time; he's tired of trying to change and not really knowing how to do that. He sees suicide as a way out, which it never should be."

Paul, who rose to fame and acclaim as drug-dealer Jesse Pinkman in the wildly acclaimed American TV series Breaking Bad, gravitated towards the JJ because he related to both the emotionally troubled character and his predicament. "There have definitely been times in my life where I was struggling to keep my head above water," says the actor. "I knew what I wanted to do but I had so many ups and downs and I felt so lonely at times. Heartache and heartbreak. And the way these four characters were presented in the script was just dead-on. They're polar opposites and yet they find themselves creating a strange, beautiful bond together. I loved the story so much."

For Paul, there was little research required to tap into JJ's beleaguered mindset. Just as his character harbors dreams to be a music star, so, at one point, did Paul. "Have I ever harbored dreams of being a rock star? Yeah! What young guy hasn't?" he smiles. "And, you know, I actually used to be a pizza delivery boy, too. It was one of my many jobs before acting took off."

The only American in the cast, Paul loved coming to the UK for the shoot, and even ended up taking Brosnan one night to see his favourite band Radiohead in concert. "I became instantly hip," laughs Brosnan, recalling the big night. "Aaron's a great tweeter; he tweeted a photograph of the two of us at the concert, and then he said, 'Look man, we've got 800 hits in five minutes!' This old dog became hip. I like Radiohead. Not as much as Springsteen or Van Morrison but don't tell that to Toni or Aaron. They adore Thom Yorke."

Chaumeil encouraged Paul to instil his own natural charm and sweetness into the role of JJ. And like his co-stars, the young American couldn't have been more smitten working with his on-screen suicidal cohorts. "I love everything about working with these guys," says the actor. "The story is about four people who have a strange bond and pretty much save each other from death, and the four of us have this amazing bond, too. I don't think we're necessarily saving each other from death – we don't have the same problems – but we get along so well. We really care for each other."

MAUREEN

"I'm not entirely sure how to phrase this. But… are you going to be long?"

Toni Collette was the first actor to become attached to A Long Way Down. Dwyer, who has known the Australian actress since they worked together on the 2006 HBO movie Tsunami: The Aftermath, brought the project to Collette's attention while she was attending the Sydney Film Festival with An Education. "I knew from the outset that we needed a brilliant actress to pull the role of Maureen off," says Dwyer, "which is why I shoved the book into Toni's hands as soon as I could."

"When I read the book, I thought it was the most exquisite story and pretty much agreed to do it immediately," says Collette. "It took a while for things to fall into place but it was worth the wait. The experience is better than I ever possibly imagined it could be. It's been amazing."

Collette describes Maureen as "extremely" socially inept but behind her meek, nervous, uncomfortable exterior, in possession of a sweet, thoughtful, kind-hearted nature. "She's a beautiful soul," observes Collette, who previously portrayed another of Hornby's depressed characters, Marcus' single mother, in the film adaptation of About A Boy. "Emotionally, she wears her heart on her sleeve. Without even really realising it, she's quite lonely and a bit sad but she has a full life taking care of her lovely son [who has severe cerebral palsy]. Of all the characters, I think when she decides to attempt to end her life, it's with a selfless motive. She just believes that her son will have a better life without her."

Having had to wait a few years before finding out who her co-stars were going to be, Collette describes them as "the perfect collection of folk". She bonded with the rest of the Topper Tower gang, and agrees they formed a tight-knit foursome during the shoot. "Everyone's so different and works differently but we gelled brilliantly," she says. "We've laughed every single day"

But the long wait also left Collette doubting whether she was right for the role. "I thought perhaps I should quit at one point," she reveals. "I felt like Maureen was a bit older, a bit more tired, a bit fatter. But the more I looked into it, the more I thought, 'I love this person.' I think she's so lovely." The actress did some research in preparation, going to the Bobath Centre in North London to observe the treatments available for cerebral palsy patients and speaking to mothers in Maureen's situation about how it affects their own lives. "The key to Maureen," says Collette, "is that she's so in love with her son Matty, she'd do absolutely anything for him." The Bobath Centre also provided consultants for the film: whenever they were filming scenes featuring Matty, a mother who has a child with cerebral palsy was always on set to provide advice and details to the director, Collette and Joseph Altin, the actor who portrays Matty.

Collette is also eager to stress that, despite the dark themes of any narrative featuring suicidal impulses come, she wants audiences to latch onto the story's cheeky humour. "It's hysterically funny at times," she says. "If you were to tell this story in a dramatic way, it might be a downer, but this film is laugh-out-loud funny. What I get out of it is how light and true it is. I always gravitate toward stories that fall both sides of the line: it's sad and it's funny and so is life. It's a buddy movie about four buddies! It's about unlikely but life-changing friendships."

Collette is full of praise for Chaumeil, citing his skills at fostering a sense of camaraderie and playfulness amidst the requisite moments of dramatic intensity. "I've worked with some directors where you feel like you're on your own," she says. "Pascal is absolutely embedded and dedicated and right there with us. It makes you feel so safe and when there is such an investment in what you're all doing, which there definitely is with us, it makes you want to give more. He's clear and confident in what he wants and what he needs."

"Toni is an incredibly skilled actress," says Chaumeil, repaying the compliment. "I never needed to tell Toni what to do. The only thing I said after the read-through was, 'Let's look for the humour in Maureen.' Toni really responded to that, and brought so much of herself to that even though Maureen is completely her creation and so different from how Toni is in real life."

"THE FIFTH CHARACTER": TOPPER'S TOWER

Production designer Chris Oddy describes Topper's Tower, the meeting point for A Long Way Down's initially suicidal quartet, as "the fifth character in the film". Shooting on the rooftop of a real London skyscraper was always going to be a huge challenge if not impossible to pull off. After an extensive search, Oddy and his team found a building – a fairly anonymous multi-use office block in the centre of London – that fit their purposes in terms of rooftop space for Chaumeil's camera moves and the relationship of said rooftop with the surrounding landscape, in particular offering a spectacular view of St. Paul's Cathedral.

Once they'd found their building, its rooftop, with modifications for filming purposes, was then reconstructed at Pinewood Studios, allowing Chaumeil to control the environment with camera angles and movements. The actors could also perform A Long Way Down's most challenging sequences without the real threat of wintry elements, hundreds of feet above ground, to wreak havoc on their performances.

The resulting set was a 12-metre square space, constructed 10 feet off the ground. "Even in the studio, you wouldn't have wanted to fall off that ledge," says Dwyer. "When the actors were on the edge of our rooftop set, they were in harnesses but they at least felt themselves being on an edge."

And they'd also had first-hand experience of the real edge. After the first read-through of the script, the four actors, Posey, Dwyer and Chaumeil had all dined together at St. John in Shoreditch and followed up their meal with a recce to the top of the building that Oddy had found to play Topper's Tower (to Posey and Dwyer's relief, the tower block is due to be demolished before their film's release: "It's not an iconic building at all, it's pretty anonymous," says Dwyer).

"We all stood there that night and took a moment and contemplated what it would be like to throw yourself off," says Brosnan. "It was palpable, that feeling. That's part of the emotional life of an actor."

In his first meeting with Chaumeil, when the conversation turned to Topper's Tower, cinematographer Ben Davis told the director they were going to have to film it on a stage. "We couldn't have achieved anything close to what we achieved if we'd done it on location," he argues. "It was a simple build but in order to capture the drama of that scene we needed a lot of angles that were off the rooftop looking back at someone standing on the edge. And we were able to do it all with our cast rather than stuntmen, because there wasn't a 1000-foot drop at the side of the set."

"There was a lot of pressure shooting those scenes, we couldn't get them wrong," says Chaumeil, who needed three days in total to shoot the film's opening sequence because of the number of shots required. "It was so important because we were introducing every character, and we also had to find the right balance between being real and being funny. You see Martin's character, he's really scared when he's on the edge, but it can't be too dramatic because then you have a hard time getting back to the comedy. It was tricky."

THE REMAINING CAST

Around A Long Way Down's Big Four orbit several key supporting characters, chief amongst them Jess' parliamentarian father Chris, played by New Zealand actor Sam Neill. "Chris is a fairly distinguished politician," explains Neill. "He has a dysfunctional family life, however. His daughter Jess is a troubled young woman, with the elephant in the room being that her sister went missing a couple of years ago leaving the family paralysed with suspended grief."

"We were really lucky to get Sam," says Chaumeil. "We didn't think we'd get someone as big as him to play Jess' father." Fortunately, Neill was coming to the UK for another film shoot and managed to squeeze a week into his schedule for A Long Way Down. "With an actor of Sam's level, that character immediately becomes more interesting. In his few scenes, you can feel that character has a heart but he's also really funny. It was a gift."

Rosamund Pike, who made such a memorable impression as the ditzy Helen in An Education, agreed to reunite with the producers for A Long Way Down, shooting a caustically hilarious cameo as Penny, Martin's former co-host, a falsely smiling presenter who turns out to have a ruthless agenda when she lands the scoop with the Topper House Four on her breakfast TV sofa. "Ros is fantastic in the film and she took her role very seriously," says Chaumeil. "She even went a few times on real breakfast shows to see how it all worked."

Tuppence Middleton was originally up for the role of Jess, and Chaumeil remembered her when he needed to find an actress to play Kathy, the tabloid journalist who tracks the foursome to Spain hoping to land her big story and has a fling with JJ without revealing her true identity. "She had to be someone JJ would find attractive and she had to have a bit of mystery," says Chaumeil. "Tuppence was great in the role."