A love triangle set during the turbulence of Paris, May 1968: it’s surely the quintessential Bertolucci subject. He’s always had an interest in stories in which political events clash with personal entanglements; witness the likes of Il Conformista/The Conformist (1970), Novecento/1900 (1976) and The Last Emperor (1987). The Dreamers, adapted by Gilbert Adair from his novel ‘The Innocents’, allows Bertolucci ample opportunity to depict the labyrinthine games of love and sex between the young protagonists, but lacks a wider insight which would have really brought the tale to life.

Matthew (Michael Pitt) is in Paris ostensibly to study French; happily, he’s also in the perfect place – and time – to indulge his passion for cinema. Falling in with Parisian brother and sister Theo (Louis Garrel) and Isabelle (Eva Green), he accepts their invitation to move into their apartment for a month while their parents are away. From there, a succession of dares lead to sexual developments which prove more emotionally complex than any of them had anticipated.

The apartment gives the drama an almost abstract air. The family has money, and yet this is a living space ready to deteriorate as the young trio spread their plates and bottles – and naked bodies – all over it. Matthew is our touchstone in this psychologically demanding situation, an idealistic young man dismayed by his inability to resist the siblings. In these stretches of the movie Bertolucci proves that he is still a master at pacing lengthy sequences involving characters operating at cross-purposes; think of the non-communicative sex scenes in Last Tango in Paris (1972), the struggles between mother and son in La Luna (1979) and the married couple traversing the North African desert in The Sheltering Sky (1990). As these games develop, we become immersed in the power-plays.

And yet, like Matthew, as they continue, we start to ask if there isn’t more that can be offered, more that we can learn. The student riots are happening, often literally, outside the window; there is a terrific moment late in the movie in which Matthew berates the siblings for their immaturity, their lack of self-reflection. And yet the movie needs more of that. We need to know why they do what they do, and how it makes them feel.

This renders the sexual explicitness difficult to read: is it gratuitous, the tired attempt of an filmmaker to titillate his audience? Or has Bertolucci become so comfortable in his lack of shame about the human body that the nakedness assumes an heroic simplicity? I was led towards the latter interpretation by the honesty, and by the assured performances from the leads.

With its Parisian apartment, its French nouvelle vague references and its frank physicality, The Dreamers lends itself to comparisons with Last Tango in Paris (1972) – and yet Last Tango embellishes its central situation by following the characters individually, outside the apartment: what we learn about Marlon Brando’s Paul and Maria Schneider’s Jeanne sheds light on their motivations. The Dreamers, by contrast, lacks an overall sense of organisation or purpose.

And yet – without giving away how the story develops and ends – I did wonder if The Dreamers might be attempting something rather more subtle, in suggesting that political commitment takes a backseat once emotional and sexual intimacy come into play. As with the terrorist subplot which keeps imposing on the terrible serio-comic romantic pursuit in Bunuel’s Cet obscur objet du desir/That Obscure Object of Desire (1977), Bertolucci might be keeping the riots deliberately in the background so as to alert the viewer to the movie’s diversion from what looks in many ways like a more significant story. However one reacts to the ending of The Dreamers, it has to be said that this is not a major Bertolucci movie – but what it does, it does very well.