Leonardo DiCaprio gives 300 per cent to his portrait of the G-man at every stage of his career. (Warner Bros.)

Once Hollywood's favourite tough guy, director Clint Eastwood has been slowly deconstructing what it means to be a macho man on the big screen. There was the reluctant cowboy of Unforgiven; the soldiers of Flags of our Fathers/Letters from Iwo Jima; the repercussions of violence in Gran Torino.

Now Eastwood has seized on the story of J.Edgar Hoover, a male archetype if there ever was one. The ultimate G-Man. The top cop. The director of the FBI who fought the Reds and brought modern forensic science to the Bureau.

Of course that wasn't the only side of Hoover, which is what makes him so compelling. Rumours of a hidden sex life and claims of cross-dressing swirled for years. Indeed if J.Edgar accomplishes anything, it's to renew the debate.

The script for J.Edgar comes from Dustin Lance Black who wrote the full-bodied bio about Harvey Milk. But where the movie Milk was vibrant and passionate, J.Edgar is stilted and repressed. Turgid. Of course living life as a gay man at Hoover's time was incredibly different. But given all the screen time the various versions of Hoover are given, we never really see inside the man.

Clint Eastwood works with DiCaprio on the set. (Warner Bros.)

Stepping into Hoover's perfectly pressed pants is Leonard DiCaprio. Like fellow superactor Tom Cruise, DiCaprio always gives 300 per cent. You can almost see the effort, the careful calculation that went into becoming Hoover. It is an amazing transformation. We see Hoover both young and old - he was little more than a teen when he rose through the ranks of the Bureau of Investigation, battling Bolshevik terrorists and bringing a new respectability to the force. The elder Hoover has a face like a defeated bulldog, all pinched lips and hanging jowls. His force of will is the consistent thread, channeled by DiCaprio.

We hear a lot of Hoover as he dictates his autobiography to a string of young agents. We see him charming Congress and bullying Attorney General Robert Kennedy. But we never quite learn what it was that drove him. Was it his overbearing mother played by the now omnipresent Judi Dench? Or was it his assistant and lifelong companion Clyde Tolson, played as a dandy Ken doll by Armie Hammer. Hammer does add a welcome bit of warmth to the picture, the one person who seems to understand and even love the man. But in later years Clyde becomes a pantomime of aging, hidden by make-up that looks like it was applied by trowel.

Eastwood's J.Edgar certainly covers too much a lot of ground. There's Hoover's rise to power, the battle against organized crime, a lengthy portion regarding the Charles Lindbergh kidnapping, the FBI's prominence in pop culture, and in the later years Hoover's vendettas against the Kennedys and Martin Luther King Jr. It all climaxes in an absurd moment as Hoover is overheard listening to secret tapes of MLK's own love life, the very moment he's being informed that President Kennedy has been shot. One wants to laugh, but Eastwood plays it straight.

J. Edgar tells us a lot about what he did, but never who he was. It feels as if Eastwood is filming Hoover at a distance, afraid to take sides. Instead he drowns his subjects in syrup - the signature Eastwood soundtrack, twinkling pianos and sobbing strings, standing in for Hoover's hollow heart. At the screening I attended, a fit of coughing broke out during one of the elder J.Edgar's speeches, perhaps an allergic reaction to cheese.

Stunning in its scope, J.Edgar is a polite profile of a man who had his way with Lady Justice. A surprisingly forgettable film about an unforgettable man.

RATING: Two perfectly pressed pocket squares out of five.