Richard Osman's Thursday Murder Club book series is one of the most successful of recent years - more than 10 million copies have been sold, all four books have broken UK sales records, and the fifth instalment will be released in the autumn.

It's no wonder, then, that the star-studded cast of the film adaptation are somewhat nervous about how fans will receive the movie.

Speaking to the BBC, Pierce Brosnan says nerves have ramped up over the past few weeks. "It's a huge responsibility when you have an audience and the world waiting to see these characters."

The film sees the usually well-groomed Irishman transform into a bearded Ron, the gregarious one-time trade union leader turned unlikely amateur sleuth, in a new Netflix movie based on the first book in the series.

Brosnan also admits he first thought of another actor when reading the part of Ron.

"I never asked Chris why he cast me," says Brosnan. "I thought: 'this is Ray Winstone, bro.'" But the actor kept any doubts to himself, and remembers thinking: "'Don't say anything, Pierce, just keep going.'"

Dame Helen Mirren's Elizabeth, Celia Imrie's Joyce and Sir Ben Kingsley's Ibrahim round out a quartet that unites to investigate murder, just as long as it fits around the local bus timetable.

The result sees the mystery-solving group living their later years at an otherwise idyllic retirement village, Coopers Chase.

Brosnan says his co-stars helped ease the nerves, and the group "had a great time" on set.

A bromance is born

It seems the 72-year-old has struck up a particularly close friendship with Sir Ben, 81, and the pair tell the BBC about how they enjoyed getting to know each other better on set.

"We'd stand around and chat about things we liked, and we discovered we both love Laurel and Hardy," Brosnan says before Sir Ben interrupts him with a rendition of the Trail of the Lonesome Pine, with which Brosnan joyfully joins in.

The pacey two-hour adventure has Steven Spielberg's involvement, through the Jaws director's production company Amblin, and is directed by Chris Columbus, of Harry Potter and Home Alone fame.

Sir Ben says that is what first piqued his interest, with the script being a final clincher.

"It's a beautiful script and it is so idiosyncratically English - it's a new old English movie."

As many readers' top choice to play mysterious group leader Elizabeth, Dame Helen, 80, admits to thinking the same when she first read the novel.

"Embarrassingly, I did. When you read that book, you think immediately, this could be a movie, and then, if it is, I wonder if they'll ever approach me to play that role, because I'd love to play it. It was sort of a bit of a miracle for me when they did."

Imrie, 73, who plays former nurse Joyce, took the opposite approach and did not read the book until they were cast.

"Dear friends of mine occasionally said: 'You know, you'd be awfully good for this, but I'm quite superstitious,'" Imrie recalls. "I didn't want to spook things. The minute I was cast, I ran down to the bookshop."

The film has received mixed reviews from critics. In a two-star review, the Telegraph's Robbie Collin called it a "nefariously lazy" adaptation that is little more than a "half-hearted parody of a whodunnit".

Clarisse Loughrey of The Independent also awarded two stars, saying the film failed to make the most of its all-star cast and "is so flimsy and digestible, it barely exists" with "each clue presented plainly, legibly, and without even a hint of enigma".

There was a more positive review from Kevin Maher of the Times, who agreed that "there is a lot of heavy exposition" but awarded the film four stars, adding: "Camp and quietly sad, a franchise is born."

A middling three-star review from The Guardian's Peter Bradshaw said that there was "much to enjoy" and "the club sometimes resembling a kind of senior-citizen X-Men group whose collective superpower is invisibility".

The cosy-crime movie will be out in cinemas for a week before being available to stream on Netflix.

Its cinematic release is somewhat limited as it's only being shown in 30 cinemas, something Dame Helen says is "disappointing".

"I think it would have done well in the cinema and I wish it was staying for a little longer," she says, adding she has "no idea" why the release is so limited.

But Osman says it's a hard time right now to get films commissioned, so he's grateful to Netflix for its support.

The first day of filming for the foursome was an emotional scene set in a hospice. For Imrie, it encapsulated a broader theme for the film.

"It was full of what hangs over the story, not in a morbid way, but we are around the bed of someone that is dying, and we're all of an age where that is going to happen," she says.

"It was the starting point, I think it gives the film some ballast," adds Sir Ben. "It's not a little comedy. It has some layers to it... a base note that runs through it."

Dame Helen agrees: "That's the great success of the books, isn't it, the way Richard combines real sadness, the reality that life involves death always… but at the same time, there is this great, natural humane comedy bubbling up all the time."

As for whether they'd return to Coopers Chase in the not-too-distant future, Dame Helen and Brosnan are enthusiastic. "Yes, absolutely," they respond in unison. This A-list ensemble's adventures, it seems, may have only just begun.