Only a handful of directors have won the Oscar twice. But Milos Forman is more than at home in the company of Frank Capra, William Wyler, Fred Zinnemann and Billy Wilder - the outsiders who beat Hollywood at its own game, the Europeans who held up a mirror to America and showed the world a side it would rather had remained concealed, writes David Parkinson.

Yet, with the likes of Taking Off, Hair, One Flew Over the Cuckoo's Nest, Ragtime, Amadeus, Valmont, The People vs Larry Flynt and Man in the Moon to his credit, it's easy to overlook the quartet of exceptional films Forman made in his Czech homeland.

So, while the retrospective that opens at the Barbican in London this week covers his entire oeuvre, it's his early career that merits review.

Orphaned at the age of eight, when his parents were murdered in a Nazi death camp, Milos Forman was raised by relatives. In 1951, he entered the famous Czech film school, FAMU, and served his apprenticeship with journeyman director Alfred Radok, before working on the Lanterna Magika multi-media presentation that was the toast of the 1958 Brussels World Fair.

Having earned a couple of screenwriting credits, Forman made his directorial debut with Audition in 1963. Strongly exhibiting the influence of Free Cinema (the movement that had spawned the British 'kitchen sink' tradition), this medium-length documentary is, in many ways, a forerunner of the ghastly PopStars series, as it follows a group of young hopefuls trying to break into the (far from groovy) Czech pop scene. It's showing here as a single feature thanks to the addition of If There Were No Music, Forman's second film, which pursues a pair of rival brass bands as they prepare for an outdoor concert.

Forman came to wider notice with his first fictional film, Peter and Pavla (1963). Adapted from the novel by Jaroslav Papousek, it's a sweetly acerbic comedy about a store detective pressurised by his parents to succeed in life and love. Although it's often been compared with Francois Truffaut's early work, the loudest echo comes from Ermanno Olmi's gentle satire on the shock of work and the everyday, Il Posto.

Making atmospheric use of the Bohemian town of Kolin and coaxing wondrously naturalistic performances from Ladislav Jakim and Pavla Martinkova, Forman began his perpetual fascination with the outsider with a sympathetic wit that would never desert him.

He reteamed with Papousek and co-scenarist Ivan Passer for A Blonde in Love (1965), which not only furthered his fondness for improvisation, but also his determination to develop (along with cinematographer Miroslav Ondricek) a non-functional camera style.

Combining sly situation comedy with charming behaviourist observation, it thoroughly merited its Oscar nomination. Hana Brecjchova excels as the small-town factory girl whose earnest (and one-sided) pursuit of pianist Vladimir Pucholt comes to a head when she follows him to his parents' house in Prague. Full of the affectionate irony that characterised Forman's early studies of naive youth, this is also a subtly acerbic social satire, although there's a more openly mocking tone to the scenes dealing with the military, the older generation and sexual manners.

He ran into trouble with the authorities with his last Czech feature to date, The Fireman's Ball (1967), which, despite its international acclaim, was pronounced 'banned forever' at the end of the Prague Spring. What begins as a gently mocking comedy of small-town manners, ends as a blazing allegorical satire on the incompetence, insularity and ideological idiocy of the state. Amidst the wealth of comic detail that surrounds the ball held to celebrate a veteran fire chief's retirement, it's easy to forget that the real theme of this socialist realist parody is the Stalinist purges of the 1950s. But the chaotic beauty contest, the theft of the lottery prizes and the discomfort of the guest of honour can all be enjoyed without a deep knowledge of Czech politics.

Forman was in Hollywood, working on the generational comedy Taking Off, when the Soviet tanks rolled into Czechoslovakia and he was forced into exile. In 1975, he won Oscar No.1 for One Flew Over the Cuckoo's Nest, the first film to take the Big Five Academy Awards since Capra's It Happened One Night, 41 years earlier. Prizes have been tumbling in ever since. He landed his second Oscar for Amadeus (1984), much of which was filmed in Prague, before winning the Golden Bear at Berlin for The People vs Larry Flynt in 1996 and the Best Director gong at the same festival in 2000 for his wrongly dismissed Andy Kaufman biopic, Man on the Moon.

After the last-minute withdrawl of Japanese backers for Hell Camp and the failure to secure the rights to Foucault's Pendulum, rumours have abounded that the 69-year-old Forman is considering retiring from movies to concentrate on his duties as Professor of Film at Columbia. But equally loud are the whispers he's developing studies of both Goya and Howard Hughes. We can but hope. . .