I have mentioned a couple of times that one of the inspirations for setting The Rainbow Orchid in the 1920s was Kevin Brownlow's brilliant 1968 book The Parade's Gone By. It featured interviews with a number of then still surviving silent-film stars, directors and technicians, and though its focus was on Hollywood, it also featured a French director, Abel Gance.

Gance was a genius of the silent era, making startlingly creative films such as J'Accuse and La Roue. But his biggest project was Napoléon, and as soon as I read about it in Brownlow's book - in the mid-nineties - I knew I had to see it.

The trouble is, Napoléon is not an easy film to see. Pretty much as soon as it had its premiere, in 1927, the film was sent out into the world cut down, reformatted, re-edited, cut again, partially lost, resized, copied and recopied, and even, in the 1930s, dubbed into an awful sound version. Audiences who went to see the the film, proclaimed as sensational on its first showing, often saw something heavily watered down at best, and an incomprehensible mess at worst. Gance's star faded and he entered a long period of creative anticlimax.

That the film has today been restored to its former glory, and reappraised into its rightful high place in film history, is almost all down to the enthusiasm of one man - Kevin Brownlow. As a young film collector in the 1950s he happened across two reels of the film and was immediately struck by its originality and style. He set out to find more, a quest that led him to the flea markets of Paris, the guarded archives of France's Cinémathèque, and far beyond - including meeting and befriending Abel Gance himself.

That process of reconstruction has never really ended, despite it enjoying huge revival showings in the early 1970s and 80s. Finally, last week, I was able to see the film myself, in a one-off screening at the Royal Festival Hall, complete with live orchestra accompaniment from the Philharmonia, with Carl Davis conducting his own score for the nearly six-hour film.

I was slightly worried that the reality of Napoléon would not live up to my expectations, having heard and read so much about it, but the film actually left me in something of a daze. Some of the impact was immediate - the stunning Brienne snowball fight that opens the film, the emotional unveiling of La Marseillaise, the sensation of the convention scene, the rapid cutting of Napoléon and Josephine's previous encounters, the victims' ball (where the men were 18th century and the women were all but 1920s flappers), and - the show stopper - the much anticipated widening of the screen to reveal Gance's innovative triptych as Napoléon's army marches into Italy. Other scenes I struggled with slightly, usually owing to my own lack of Napoléonic knowledge - the scenes in Corsica being a case in point, but not much else besides that.

The music was a huge part of the experience - what a feat of stamina for the orchestra, and Davis, to keep going for so long, never mind keeping in sync with the film (including some perfectly timed cannon shots). It was a couple of days before some of the musical themes faded from my head.

What is stunning about the film is not so much the story (interesting as it is), but the way it was told. Gance freed the camera - it was a snowball in flight, it was attached to sleds and guillotines, it swung on a pendulum and ran around attached to an operator's chest. The cutting was tight and sometimes startlingly rapid. At other times the screen was charged with two or three images on top of each other, wonderfully composed. The scope of the film, as you'd expect with the subject, was epic, a feeling reflected in the triptych, sometimes displaying a vast panorama with horses galloping from one end to the other, and sometimes parading two or three juxtaposed images. At one point the three screens were tinted with the Tricolore. It was immensely impressive.

Brownlow's story of the reconstruction of Napoléon is as fascinating as the film itself, and a couple of days ago I attended a talk by him at the British Flm Institute, though much of that story is written in more detail in his very absorbing book Napoléon: Abel Gance's Classic Film. It was really a triumph of will to put the film back together, especially in dealing with the often obstructive Cinémathèque, and even sometimes with Gance himself. One particularly poignant image is of Gance, 89 years old, watching alone from his hotel window as the audience below, at an outdoor revival in Telluride, gasped in astonishment at the revived masterpiece.

At the BFI someone asked if Stanley Kubrick, given his interest in Napoléon, had ever approached him about Gance's version. Brownlow - after not quite hearing and saying "Stan who?" - causing much laughter - replied that Kubrick had 'phoned him, asking for a print. "You're a man of the cinema", said Brownlow, "you have to see it on the big screen!". Kubrick, to his knowledge, never did. When informed that Baz Luhrmann had recently been chosen to revive Kubrick's project he rolled his eyes; when he was told that is was for television, he groaned!

There are many other stories, not least of the actors, particularly Albert Dieudonné, who played Napoléon, and never again stepped out of his shadow (on a trip to London later in life he said "I do not want to visit Trafalgar or Waterloo!").

If you get the chance to see Abel Gance's Napoléon - do so (it's next showing in Amsterdam, in 2014). Do not see it on DVD - there is one available, and Brownlow warned us not to buy it from the BFI shop; he wanted his name taken off it, "but instead they made it bigger" he sighed. This is a spectacle - it demands a big screen, live music, and an audience. A true emperor of film.

Special thanks to Linda Wada for her excellent company on this cinematic expedition!