Even by Cannes standards, this year has garnered some bizarre sights.

Two tanks rolling down the street to promote The Expendables III. A naked Gérard Depardieu being strip-searched, in a special beach-side screening of his new movie Welcome To New York. Pamela Anderson playing backgammon with Vivienne Westwood (all for charity). And Ukrainian prankster Vitalii Sediuk crawling underneath an understandably distressed America Ferrara's dress on the red carpet for How To Train Your Dragon 2.

Still, there can be no stranger spectacle than watching middle-aged film industry types reduced to quivering teenagers when Spandau Ballet stars Tony Hadley and Steve Norman took to the Plage Royale beach venue to perform an acoustic set. Hadley, who arrived on crutches after a recent knee operation, crooned his way through the band's seminal songs, Gold, True and Through The Barricades, not to mention a well-received cover of David Bowie's influential Starman, while Norman more than demonstrated his guitar-playing skills.

While it's not unusual for the music biz to latch onto the film festival - Rita Ora and Côte d'Azur regular Kylie Minogue are also both performing on the Croisette this week - the Spandau boys were here on a mission: to promote their new film, Soul Boys of the Western World. A lively documentary about the band's formation, evolution, break-up and eventual reunion, it's been culled from over 450 hours of archive footage, painstakingly put together by debut director George Hencken.

Recalling how the band formed as part of the New Romantics explosion in the early 1980s, arriving out of London nightclubs like Billy's and the Blitz, it features recollections from each band member: singer Hadley, sax-player Norman, drummer John Keeble, bass player Martin Kemp, and his brother Gary, guitar player and chief song writer. But as Hadley told me earlier in the day, it's not just a thirst for all things retro that's driving the enthusiasm. "People see an awful lot in this film."

It was during the band's Reformation tour in 2009 - when a montage of old clips played on a video wall during the performance of Round And Round - that the idea was hatched. "It went down so well with the audiences, it was the spark that led onto making an archive-led film," says a tanned and silver-haired Martin, 52, who also made the trip to Cannes. In came Hencken, who cut her teeth as a producer working for director Julien Temple, including the clip-driven London - The Modern Babylon.

Early on, Hencken showed the film to Temple (famed for his work with The Sex Pistols on The Great Rock'n'Roll Swindle). "At that stage it was three hours long," she recalls. "His comment was 'That felt every single second of three hours long!'" While the punk-loving Temple may not have been appreciative of the band's electro-synth sound, there was a generation that grew up on Hadley and co. "There are plenty of people my age," says the 46 year-old director, "who had their first kiss to True."

Interviewing each band member separately, more than once - we see no talking-heads, refreshingly, but just hear resulting voiceover - it could've been all too easy to slip into a nostalgia fest, but Hencken avoids that, not least by placing Spandau Ballet in a social context. "She uses the band as the protagonist to take you through the 80s," says Martin. "So you don't just get to see the band's home movies...it's not like that. You get to see what it was like in the 80s."

The tricky subject of the band's demise is also covered, which began as Martin and Gary took roles in 1990's The Krays, playing London's notorious gangsters Ronnie and Reggie Kray. Curiously, it was recently announced that Tom Hardy was hoping to play both of the feared twins in a forthcoming biopic. "Good luck to him," laughs Martin. "I had a hard enough time remembering the lines for one of them."

While Martin went on to spend four years in Eastenders, the remainder of the band found real drama in the High Court. A bitter - and very high profile - dispute arose when Hadley, Keeble and Norman attempted to sue Gary Kemp for unpaid royalties. "I think it was very traumatic and left some very deep scars," says Hencken, who broaches the topic in her film but estimated all five found it difficult to talk about. To their credit, the band managed to put the dispute behind them when they reformed in 2009.

"In the past, I'd probably not been too pleasant to Gary," the 53-year-old Hadley explains. "We met, we both said our piece, and then said - over a pint of beer with John Keeble as the referee - 'Do you think this can move on? Do you think we can make this work again?' And we both agreed that we could, but we wouldn't talk about what's happened. And what's happened has happened, and we move on. And I'm a great believer in that. S*** happens with bands"

While Keeble and Gary Kemp weren't in Cannes, it was more to do with French transport strikes keeping them grounded than any greater conspiracy. Following on from the film, plans are afoot for new material and an overseas tour. Plans are afoot for new material and an overseas tour.

"We all like each other again, which is fantastic," smiles Hadley, "We're grown-up guys. And there's no bullshit between us." Which for Cannes is quite a feat.

Soul Boys of the Western World will be released later in the year.