We tend to associate Scandinavian fare these days with hardboiled TV detectives and gritty big-screen thrillers.

But now and again we're reminded of the Nordic sense of humour, which happens to be decidedly eccentric.

This outlandish Swedish comedy is based on the bestseller by Jonas Jonasson, with shades of Forrest Gump and Woody Allen's Zelig in its proposition - the unlikely life and times of a man caught up in the momentous events of the 20th century. In place of the good nature of the first of those films, and the sophisticated wit of the second, this plumbs for absurdity and farce; at times the humour is a little too broad; but when it hits the mark it's deliciously twisted, fantastically funny and quite irresistible.

The film opens with a deadpan statement of outrageous intent, as the elderly Allan Karlsson (Robert Gustafsson) exacts revenge on the fox which killed his cat, by hiding some sticks of dynamite inside a pack of sausages. His cat was, appropriately, named Molotov.

The expected result lands him in a retirement home, which is not Allan's cup of tea. As the staff prepare to celebrate his 100th birthday, this indefatigable chap casually climbs out of the window, takes himself to the bus station and gets the first ride out of town.

But Allan has inadvertently boarded the bus with a suitcase belonging to an aggressively twitchy skinhead he encountered at the station. The case contains a great deal of illicit cash. And for the next two hours murderous crooks and an inept policeman will be on the old man's trail.

"Many have shouted at me over the years, from stationmasters to dictators," Allan declares. While on the road, he recalls the famous people he's rubbed shoulders with - Franco and Stalin, Truman and Reagan, Gorbachev - and the historic moments in which he's played an unlikely role: the Spanish Civil War, the invention of the atomic bomb, the Cold War and the fall of the Berlin Wall.

It's ridiculous that such an ordinary man, without conspicuous intelligence or charm, should have such encounters. Moreover, Allan isn't particularly sane - that fox is only one victim of his penchant for explosives, and his childhood and early life contain enough trauma to offset anyone for life.

Yet he has an innate common sense, and a way of nonchalantly accepting any situation that makes him a surprising friend and ally. While Gump lived through his mother's dictum that "life is a box of chocolates", Allan frequently pulls out his mother's deathbed observation that "life's what it is, and will be what it will be."

His stoicism, while all around him is chaos, is beautifully captured by Gustafsson. One of Sweden's most popular comedians, as well as an actor, he easily delineates the character from creepily pale teenager through to crinkled triple figures, never quite allowing us to be sure what is going on in his head.

The present-day pursuit, which descends into cliché, offers the film's less interesting dimension. The past is much more satisfying, offering impressive cinematography (Allan as Cold War spy being surprised by a submarine is a stand-out moment) to accompany the off-the-wall scenarios. Incidentally, Allan's funniest companion is a fictional one: Albert Einstein's idiot brother, a fellow gulag inmate, who can't compute Allan's simple plan for escape.

Adapter and director Felix Herngren keeps things moving pretty seamlessly between the past and present, has a good eye for the madcap, and maintains a constant breezy mood.