During a turbulent and contentious term in power spanning almost 50 years, J Edgar Hoover was instrumental in the fight against mounting criminality on the streets of America.

In 1924, he was appointed director of the Bureau of Investigation, which became the FBI, and he threw his weight behind the latest developments in forensic science.

Hoover championed the creation of a centralised fingerprint database that allowed the agency to track offenders across states.

His achievements were considerable but his methods were heavily criticised, including supposed heavy-handed treatment of suspects and secret dossiers on important figures, such as the presidents and their wives, which could be used to strengthen his position on Capitol Hill.

As Hoover, played with scenery-chewing gusto by Leonardo DiCaprio in Clint Eastwood’s handsomely crafted and slow-burning biopic, tells a close ally, ‘No one freely shares power in Washington.’ Eastwood crafts a meticulous and elegiac portrait of the man, whose professional travails were almost as fascinating as the swirl of rumours surrounding his close relationship with FBI assistant director Clyde Tolson.

Following Hoover’s death, Tolson accepted the flag draped over his mentor’s coffin and inherited J Edgar’s estate.

They are buried close to each other in the Congressional Cemetery.

Screenwriter Dustin Lance Black, who won an Academy Award for Milk, underpins his history lesson with a tender and chaste romance between the two men.

The film opens with Hoover (DiCaprio) clinging to power, assisted as ever by loyal secretary Helen Gandy (Naomi Watts).

He begins to dictate his memoirs to Agent Smith (Ed Westwick) and drifts back in time in hazy reminiscences to the 1919 bombings which sent shockwaves through Washington DC.

With Clyde (Armie Hammer) by his side, Hoover becomes embroiled in the ill-fated search for the missing infant son of aviator Charles Lindbergh (Josh Lucas) and clashes with Robert F Kennedy (Jeffrey Donovan).

Away from the corridors of power, Hoover strives tirelessly to impress his domineering mother, Anna Marie (Dame Judi Dench), who instructs him to hold firm when others doubt him: ‘Faith, Edgar, don’t wilt like a little flower.’ J Edgar is overlong at 136 minutes and the ageing make-up used to transform DiCaprio into a liver-spotted septuagenarian isn’t convincing.

However, his performance is electrifying, eyes burning bright as he tells Clyde, ‘Sometimes you have to bend the laws a little in order to keep your country safe.’ Hammer cuts a fine figure as the loyal protege and Watts makes the most of her small but perfectly formed role.

Dench offers sterling support, sending a chill down the spine as she pointedly makes clear her views on homosexuality to her boy: ‘I’d rather have a dead son than a daffodil for a son.’ The love story, which culminates in a kiss in a hotel room and an unconventional declaration of feelings, is handled with sensitivity and restraint – two qualities which eluded the great man.

• Release Date: Friday 20 January 2012
• Certificate: 15
• Runtime: 136mins