This is what French director Guillaume Nicloux has done in his new film Thalasso, blurring the line between fiction and documentary and offering fresh insight into two of modern France's best-known but provocative figures.

In the movie, which hit French cinemas on Wednesday, Depardieu, 70, celebrated for his talent as much as his love of excess, meets Houellebecq, 63, famed for his polemical and visionary novels, at a thalassotherapy seawater spa in Normandy.

Both men, who play themselves, are not in the least convinced by the spa treatment and are particularly frustrated by the ban on smoking and alcohol at the facility.

Houellebecq meets Depardieu while he is smoking in secret and, clad in regulation white fluffy dressing gowns, they begin meeting in their rooms to enjoy good wines and discuss life, death and politics.

'Being more themselves' 

“I wanted both Michel and Gerard to go into a creative process that is very particular. There was a script, a written document, but also everything that happened on the sidelines,” Nicloux told AFP.

“What interests me is exploring areas that are ambiguous and sometimes troubled, and the advantage of this process is it gives them the chance to be even more themselves than if I had made a documentary.”

Nicloux has worked with both men before and in 2014 made a film called “The Kidnapping of Michel Houellebecq” where the author is kidnapped during a promotional tour. In “Thalasso” Houellebecq again meets with his cinematic abductors.

The pair become an unlikely comic duo, with the cynical, mordant humour of the wiry Houellebecq a sometimes hilarious foil to the massive Depardieu's extravagant panache.

“I should have been a candidate in the elections,” muses Houellebecq, sitting on a lounger by the pool. “I did not know that (President Emmanuel) Macron would mess up so fast. I think I would do better.”

“All this politics is shit,” interjects Depardieu, his dressing gown open to reveal his ample chest. “I don't want to be their stooge. They are all the same, they say the same things.”

'Shame of France' 

Houellebecq shot to fame with nihilistic novels depicting misogynistic men trapped in loveless existences and hooked on casual sex.

His latest novel Serotonin – about a hard-drinking and depressed employee at the agriculture ministry in Paris who discovers the hardship of rural France – became an instant bestseller after it was published earlier this year.

His previous novel Submission, published in French on the same day jihadists attacked the satirical weekly Charlie Hebdo on January 7, 2015, predicts that France will elect a Muslim president in 2022 and be subject to Sharia law.

But in a sign of his importance within the cultural establishment that he nominally scorns, Macron in April awarded Houellebecq the Legion d'honneur, France's top honour.

Depardieu, the star of classic French films The Last Metro and Cyrano de Bergerac, has in recent years been in the spotlight as much for his private life as for his career.

Prosecutors in June closed a case into allegations Depardieu raped a young actress due to lack of evidence. He had always maintained his innocence.

In 2013 Depardieu sparked a huge outcry by taking Russian nationality to protest a proposed tax hike on the rich in his homeland.

Always defiant, Depardieu is shown in the film smoking and wearing a gilet jacket emblazoned with the double-headed eagle crest of Russia.

“I want to say that you are the shame of France,” a fellow guest tells the pair in the film.

Satirical weekly Charlie Hebdo plastered its front cover on Wednesday with a giant, big-breasted Depardieu apparently having sex with a waif-like Houellebecq holding a cigarette, and asked: “What cinema will we leave for our children?”