Where Eagles Dare isn’t just any war movie.

Barry Norman once described it as “the best film of its kind ever made” and it has a large number of celebrity fans including directors Steven ­Spielberg and Quentin Tarantino.

It was also the zenith of Alistair MacLean’s career. It was the Glasgow-born writer’s first original screenplay and the roots of the film go back to late 1965, when US producer Elliott Kastner was keen to get MacLean to write a World War II adventure.

At that point, MacLean had written 10 novels, including HMS Ulysses in 1955 and The Guns of Navarone in 1957.

However, his last book had been Ice Station Zebra (1963) and, since its publication, MacLean had given up writing to run three hotels he owned.

Richard Burton and Clint Eastwood scope out hideaway in Bavarian Alps

Kastner met MacLean at the Scot’s house in Hazlemere, Surrey, in October 1965, and a deal was struck in which the writer received an advance of $10,000 to be followed by a further $100,000 on completion of the first draft.

MacLean was given the rights to novelise the film and Where Eagles Dare proved to be the most profitable thing he ever did.

His estate receives royalties from the book and the film to this day.

By March 1966, MacLean had written a draft screenplay ­entitled Adler Schloss, German for Eagle Castle. Kastner didn’t like the title and took a line from Shakespeare’s Richard III – “Where eagles dare to perch” – to create the title.

The director, Brian G Hutton, helped Kastner refine the script.

For the lead role of Major John Smith, Kastner planned to cast Welsh actor Richard Burton, who was still considered a box office draw despite problems with alcohol.

Other actors considered for the part included Michael Caine and Marlon Brando. Eventually, Kastner opted for Burton, who was offered a flat fee of $750,000 plus 10 per cent of the film’s profits. However, the actor wanted a say in casting.

It had been Hutton’s intention to cast Leslie Caron as British agent Mary Ellison but Burton wanted Scottish actress Mary Ure as
Ellison. Ure was the wife of actor and writer Robert Shaw, and had worked with Burton on Look Back in Anger (1959).

It was also rumoured that Ure and Burton had had an affair some years before. Burton’s wife Elizabeth Taylor was aware of the past relationship and this was supposedly the reason she frequently visited the film set.

Hohenwerfen Castle was used as Nazis' mountaintop fortress Schloss Adler

MacLean’s script involved Allied agents infiltrating the “Schloss Adler” – a huge fortress sitting atop a large plug of volcanic rock and accessible only by cable car.

The production team found the ideal location – the castle at Hohen Werfen, situated on top of a rock overlooking Werfen in Austria, about 25 miles from Salzburg.

The only snag was that it didn’t have a cable car.

The problem was solved by filming the lower cable car scenes at Ebensee, 31 miles away, and creating a full-sized working cable car station in a soundstage at MGM Studios in ­Borehamwood, complete with two replica cars to those at Ebensee.

Some cable car scenes were also shot on the backlot at MGM and inside the studio, using miniatures.

The screenplay called for a number of stunts including high falls, a fight on top of a cable car, chases and explosions galore, so a total of 65 stunt performers were hired.

One, Alf Joint, doubled for Burton in most of the action scenes. Hutton later commented that the film should really be billed as “Where Eagles Dare starring Alf Joint” with a few select close-ups by Burton.

Where Eagles Dare

Clint Eastwood – Lieutenant Morris Schaffer in the film – also once remarked that it should have been titled “Where Doubles Dare”.

Shooting started in Austria on New Year’s Day 1968. The film opens with a panoramic view of the ­snow-covered Bavarian Alps and Ron ­Goodwin’s theme starts with just a few beats of a snare drum.

A tiny dot appears in the exact centre of the screen and as it flies directly towards the camera, we discover that it is a German Junkers.

The story then emerges as we see the troops preparing for their ­parachute jump into action.

Burton’s Major Smith and ­Eastwood’s Schaffer are leading a crack team to recover a captured US general being held in the German stronghold. The mission is full of thrills, double crosses, evil and thickly accented Nazi officers, goon thugs and some of the best wartime action film scenes ever.

The motorcycle and sidecar scenes were shot with stuntmen doubles intercut with studio shots of Burton and Eastwood, while real flames were added in front of the motorcycle in the studio.

Glasgow-born author Colin Barron penned the screenplay

The script originally called for Burton to drive the motorcycle and Eastwood to sit in the sidecar. But the American suggested they swap places as Burton was too drunk to control the bike.

Burton’s alcoholism was to be a problem during the production, as he would often sit up all night drinking while wearing his Nazi uniform, resulting in him being unfit for filming the next day.

At one point, his drinking buddies Richard Harris and Peter O’Toole arrived on set, and the three of them disappeared on a bender lasting days.

As Burton was a chain-smoker and very unfit, he could not climb even a few feet of rope, and clever camera work and a moving ­platform were required to allow him to keep up with Eastwood.

The cable car fight scenes were performed for real using three stuntmen, with a second cable car fitted out as a camera platform and almost as dangerous as they looked, although the stuntmen were attached to the cars by hidden steel cables.

For the scene where Smith prepares to jump from one car to another, the ascending car in the background was a two foot-high miniature which was added using blue screen technology.

The WWII flick was a box office smash

The exploding cable car was real, and the cables had to be covered with asbestos to prevent them being damaged.

Where Eagles Dare premiered in the UK on December 4, 1968 and was hugely successful, making $21million against a budget of $7.7million.

Kastner and Jerry Gershwin’s production company, Winkast, made nine more films including When Eight Bells Toll (1971) – a Bond-style action thriller written by MacLean, based on MacLean’s 1966 book and the only one of his novels to be set in his native Scotland.

Burton continued to be dogged by booze problems and died in 1984. Three years later, MacLean died in Munich, after a series of strokes, at the age of 64.

The men are buried a few paces apart in Celigny, Switzerland.

Ure also suffered from bouts of heavy drinking and in 1975, she died in London from an overdose of barbiturates.

A remake of Where Eagles Dare has been mooted over the years but as the original achieved ­excellence in so many areas, it is hard to see how it could be bettered.

  • Colin M. Barron's new book Battles on Screen: World War II Action Movies is out now. For more information and the author's other published work, visit colinbarron.co.uk or extremispublishing.com.