In The Last King of Scotland, an adequate thriller redeemed by Forest Whitaker’s sensationally good turn as Idi Amin, freshly qualified Scottish physician Nicholas Garrigan (James McAvoy) arrives in Uganda in 1970, ravenous for adventure. Under the rigorous and vaguely romantic tutelage of a lithe blonde with a flabby marriage and a thick braid hanging delectably over her shoulder (helplessly played by Gillian Anderson in stock Hollywood shorthand for a help-the-natives do-gooder), young Garrigan, wearing pointy shirt collars and a Me Decade smirk, makes a brief stab at caring for the rural poor. But he’s too feckless for the job, and soon a fateful encounter with a cow, a Maserati and the new president rescues Garrigan for more glamorous pursuits as personal physician to Amin, who has such a thing for Scotland that he saddles his many children with names like Campbell and Mackenzie. When her prescient warnings fall on deaf ears, the blonde departs with a withering backward glance, and thus do the good times roll for Amin and Garrigan — two men gifted, with an unerring talent for saying all the right things and making all the wrong moves. The difference being that one is responsible for the deaths of 1.5 million of his people.

The Last King of Scotland deals with real events filtered through Giles Foden’s 1998 novel, in which Garrigan serves as a composite of numerous white advisers with whom Amin surrounded himself, and mercilessly cut off when they no longer served his purposes. This is a first excursion into narrative features by director Kevin Macdonald, whose impressive but hyperventilating Touching the Void, a tale of mountain survival, and One Day in September, which replayed the Palestinian massacre of Israeli athletes at the Munich Olympics in 1972, were basically thrillers in documentary disguise. Working with fictional material seems to have unsettled Macdonald, for the action sequences feel hard-working and awkwardly derivative of Under Fire, Salvador and other superior thrillers about Westerners entangled in the legacy of imperialism. An audience with even the most cursory knowledge of the Ugandan conflict will find itself way ahead of the hapless protagonist caught up in a bloodbath spinning out of control; yet here, as is often the case with films about the Third World, Peter Morgan and Jeremy Brock’s expository screenplay doesn’t trust us to have even the most rudimentary familiarity with the rise and fall of one of the world’s most notorious despots, let alone those who put him in place. It falls to a diplomat, played with ferretlike cunning by Simon McBurney, to be the ventriloquist of two-faced English colonialism. “He’s got a firm hand, the only thing Africa really understands,” he says, priming us for the imminent volte-face in which the British Embassy begins plotting the ouster of a hand grown so firm that even the willfully myopic Garrigan, increasingly compromised by Amin’s escalating reign of terror, can’t ignore its excesses.

McAvoy’s deftly drawn Garrigan, callow at first, then exponentially freaked by his own unwitting role in the sudden disappearance of dissidents and innocent bystanders, makes a compelling stand-in for the Ugly American growing an eleventh-hour conscience. But this versatile actor, last seen as Mr. Tumnus the Faun in The Chronicles of Narnia, gracefully cedes the limelight to Whitaker, whose cunningly chameleon performance makes us see how the mercurial Amin could so smoothly pull the wool over the eyes of a highly educated young Scot, not to mention an entire nation. Prankish, entranced by a good fart, witty and politically savvy, Whitaker’s Amin can be the capering monkey or wild-eyed tyrant seen in countless television newsreels. But he’s also much more — a high roller overcompensating for a dirt-poor childhood, an astute manipulator of the West who hijacks a Palestinian plane hijacking for his own political purposes, and finally a madman whose careening paranoia will undo his country and himself. Whitaker humanizes Amin without in any way excusing his manipulative seductions or his appalling brutality, and he emerges as a tragic template for the whole raft of African tin-pot dictators who have followed him, their promise misshapen by a long history of poverty and colonialism, and by the premature acquisition of unchecked power.

THE LAST KING OF SCOTLAND | Directed by KEVIN MACDONALD | Written by PETER MORGAN and JEREMY BROCK, based on the novel by GILES FODEN | Produced by ANDREA CALDERWOOD, LISA BRYER and CHARLES STEEL | Released by Fox Searchlight Pictures | ArcLight, NuWilshire.

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