Another shot of Scotch on the rocks with a splash of wit

Jonathan Romney raises his glass to 'Whisky Galore!' on the eve of its re-release

The words Ealing Studios traditionally evoke all that's quintessentially English in cinema. Yet one of the studio's most enduring successes is anything but English. Think of screen Scottishness, and chances are you think of Alexander Mackendrick's Hebrides-set comedy Whisky Galore!, filmed in 1948 and rereleased this week.

Buoyant, anti-authoritarian and more than a little anti-English, Whisky Galore! is set in 1943 on the apocryphal Hebridean island of Todday. One dreadful day, the whisky runs out, causing community morale to plummet – until the islanders learn of a ship wrecked nearby, carrying a huge consignment of their beloved tipple. Naturally, they regard the cargo as fair game and help themselves – in defiance of the island's Home Guard commander, the blustering Englishman Waggett (Basil Radford).

Seen today, Whisky Galore! stands out as depicting Scottish island culture in a no-nonsense, caricature-free fashion. Todday may be peopled with larger-than-life figures – some played by leading Scottish actors including Gordon Jackson and James Robertson Justice – but the film sounds a striking note of realism, not least because much of the cast comprised the islanders of Barra, where the film was shot.

It was adapted from a novel by the fervent Scottish nationalist Sir Compton Mackenzie – born, in fact, in Hartlepool – who appears as a skipper in the film. Mackenzie based his Whisky Galore on a true incident. In 1941, a freighter, the SS Politician, ran aground near the island of Eriskay with a cargo of 22,000 cases of scotch. The islanders eagerly seized the treasure trove, while Mackenzie, local Home Guard commander at the time, turned a blind eye.

As for the film, scripted by Mackenzie and Angus MacPhail (an Englishman), it was completed altogether against the odds. Ealing's head of publicity, Russian-born Monja Danischewsky, was getting bored, so studio head Michael Balcon offered him the chance to produce a film – provided it was shot on location. Danischewsky gave his first directing job to US-born, Glasgow-raised Mackendrick. Balcon was initially unimpressed by the script, but Mackendrick and Danischewsky persuaded him to let them set up shop on Barra. But the summer of 1948 brought heavy rain and gales, and the shoot ran five weeks over its planned 10-week schedule, while the budget more than doubled.

The first cut of the resulting footage didn't please Balcon, but Charles Crichton – director of Ealing's The Lavender Hill Mob – stepped in to re-edit it. Whisky Galore! premiered in London in June 1949, and tickled the critics: the Evening News predicted the film would "put new spirit into jaded British audiences, with not a trace of a hangover". Box-office success was moderate in England, rather better in Scotland. But the film achieved major success across the Atlantic – where, to assuage pieties about drink, it was renamed Tight Little Island. It was also a hit in France, where the title's literal translation came out as Whisky à Go-Go, thereby coining a name for a multitude of nightspots. Not so keen, however, were the teetotallers of Denmark, who threatened to boycott any cinema that showed the film.

Indeed, modern viewers may be surprised to see how enthusiastically pro-booze Whisky Galore! is. It's a celebration of what, the film reminds us, comes from the Gaelic uisge beatha – the water of life.

There's much witty debunking of picture-book Scottishness. Photographed by Gerald Gibbs, the film begins with footage of sea crashing on rocks and images of lobster-catching, net-weaving and the like, in a nod to such documentaries as Robert Flaherty's Man of Aran. Then comes a mischievous gag, as the narrator (Finlay Currie) tells us that the islanders are "a happy people, with few and simple pleasures" – and as child after child after child scampers into view, we can guess what some of those pleasures might be.

In its discreet way, this is quite a sexually charged film, due in no small part to English actress Joan Greenwood, whose velvety breathiness is one of the most seductive sounds in British cinema. In one scene, a suitor courts Greenwood's Peggy Macroon on the beach; flirtatiously lowering her eyelids, she says: "If you want to be cheeky, you must be cheeky in the Gaelic." He does, and the interpolated shots of dunes and waves before the couple go home tell us he achieved the desired result.

Whisky Galore! has no protagonist as such: the "hero" of this ensemble piece is the island community. If there is a central figure, it's the likeable but pompous Waggett, played by Basil Radford. With his stuffed-shirt incompetence, Waggett is a prototype for Arthur Lowe's Captain Mainwaring in Dad's Army.

Waggett's high-minded but spoilsport attempt to foil looting makes him the butt of the film's comedy. But the character caused tension between Mackendrick and his producer: while Danischewsky took the islanders' side, the Glasgow-raised director disapproved of their anarchic actions and sympathised with Waggett. Mackendrick later said: "I began to realise that the most Scottish character in Whisky Galore! is Waggett the Englishman. He is the only Calvinist, puritan figure ... and all the other characters aren't Scots at all; they're Irish."

Whisky Galore! has long been viewed as one of the more authentically Scottish of British films – although hardcore cinephiles tend to get more dewy-eyed about the island films of Michael Powell and Emeric Pressburger, The Edge of the World and I Know Where I'm Going!. Mackendrick's film left its mark on a later hit, Bill Forsyth's Local Hero, although for critic Philip Kemp – author of Lethal Innocence: The Cinema of Alexander Mackendrick – a truer descendant is The Wicker Man.

Never pure comedy alone, Whisky Galore! also has genre shades of pirate adventure and war drama – with its snooping customs officers resembling fedora'd and raincoated Gestapo men. ("I only laugh at things that have some undercurrent of something deadly serious," Mackendrick once commented.) It's such pithiness that makes the film so lasting, where some other Ealing comedies now feel uncomfortably cosy. Mackendrick's comedies – notably The Man in the White Suit and The Ladykillers – are without a doubt at the sharp end of the Ealing spectrum. "The ruthlessness of the comedy keeps it fresh," says Philip Kemp. "Whisky Galore! ends with the Basil Radford character being quite ruthlessly shafted."

Mackendrick later forged a transatlantic career, and in 1957 made the Hollywood classic Sweet Smell of Success, a dissection of the gossip press bitterly relevant today. His directing career foundered in the late 1960s but he went on to teach film in California up to his death in 1993.

Long neglected as an auteur, Mackendrick – whose centenary is celebrated next year – is revered by film-makers including Martin Scorsese, the Coen brothers and Stephen Frears. He himself always disparaged what he called the "utterly unjustified cult of the director", but his own hands-on perfectionism made him one of the most enduring British talents. Witness Whisky Galore!, which this week will have audiences raising a glass – Slainte mhath! – once more.

Whisky Galore! is rereleased on Friday