It's not hard to see why the critics disliked Ryan's Daughter so much. Films like Midnight Cowboy and Easy Rider had come along and made lots of money and won lots of awards. Therefore Ryan's Daughter, a three-hour, 70mm epic must have seemed like something of a fossil – it certainly wasn't hip or trendy. But while Midnight Cowboy and Easy Rider haven't dated especially well, Ryan's Daughter seems timeless.

That's not to say that Ryan's Daughter is without its faults. The story is wafer-thin, some of the writing (surprisingly for Robert Bolt) is lacklustre and the film runs out of steam before the end. But I'm more than able to forgive the film its faults, as it contains some wonderful scenes and some of the greatest visuals in cinema.

My fondness for Lean's much maligned film is secured in the first few frames. In a long wide shot we see a cliff with a microscopic figure running towards the edge. Then we see the film's heroine, Rosy Ryan (Sarah Miles), chasing a black umbrella that is floating down towards the sea. It's a breathtaking start with some of the best photography committed to film – the skies, in particular, are gorgeous.

And it's the start of the film that I enjoy the most. At the beginning the film is quite light and it has lots of energy. It also presents you with a central character who is full of hope for the future – I like the way Rosy, skipping along to Maurice Jarre's magnificent score, tosses her trashy romantic book into the sea, thinking that she wont have to live vicariously through other people anymore. And then when this is cut against Charles (Robert Mitchum) arriving on the outskirts of the village by bus, you realise what everything means – Rosy's white knight is arriving.

But the film doesn't stay light and breezy for long. In fact, things go downhill on the wedding night – after expecting great things from her husband and her first sexual encounter, Rosy gets very little from Charles. It's not like it is in the books she read. A new world hasn't opened up. She hasn't been tranformed. Everything is the same. No, in fact, everything now is worse, as reality has come crashing down; everything seems so drab and dreary, especially her husband.

After this you're introduced to Major Doryan (Christopher Jones), a shell-shocked English soldier who's been sent to Ireland. Right from the first moment you know he and Rosy are going to get involved. Therefore it's a good decision on Lean's part not to delay the inevitable. And I think the scene in the pub where Rosy and the Major meet and begin their affair is easily the best in the film, and certainly one of my favourites in cinema. It's just so imaginatively done. I mean, it starts off routinely with the passionate Rosy eyeing the officer from afar (although I must say that Miles' performance is these moments is perfect - she communicates all the feelings and emotions without having to say a word), but as Michael (John Mills, playing the village idiot) begins tapping the pub booth with his foot it develops into something extraordinary. The music builds and the sound effects kick in, and as the Major shakes and shambles as he's transported by the banging back to the trenches, the scene turns into a frenzy. And as the Major dives under the table, hearing explosions ringing in his head, and as Rosy compassionately takes his hand, both characters silently reveal themselves to each other; their kiss is as much a product of mutual sympathy as it is passion - without saying a word each has been laid bare, and now, for better or worse, they're tied together.

Another great scene is Rosy and the Major's first sexual encounter. It's done without any dialogue (well, until Rosy has experienced not one but two orgasms) and again it's impeccably shot. And although I'm sure all the critics scoffed at the nature shots, Lean makes it work. And Lean makes it work because he was a genuine romantic. I mean, the reason why the vast majority of romantic films are risible are because they're not sincere – they feel incredibly cynical. But Lean can film a sex scene with shots of forest canopies and not make it laughable. But the scene also works because of Miles' superb acting. Her face captures all the trepidation and excitement that such an encounter would inspire. Just take the moments when they enter the forest. You can see that this is finally what Rosy has been dreaming of.

It's actually criminal that Miles didn't win an Oscar for her performance (she was nominated). She makes Rosy, a woman who is cheating on her good-natured husband, both despicable and understandable – it's to Miles' credit that she isn't afraid to show Rosy's ugly side; sometimes she's a petulant brat.

And I also think that Mitchum's performance is underrated. He makes a dull character interesting. But I think it helps if you're familiar with Mitchum's work. I mean, it's strange to see the original Max Cady play a cuckold. And it's even stranger to see him as a premature ejaculator and a man who gets beaten up.

And although his performance gets a lot of stick, I think Christopher Jones is fine in the film. He certainly looks the part. And although a lot of his dialogue had to be cut because the man was a mess on set, it actually works for the character. With hardly any dialogue it make his romance with Rosy a lot less banal – it gives it a bit mystery. Plus, what would an English officer and a poor Irish schoolteacher's wife have to talk about? The relationship makes much more sense as a sexual one – Rosy may love her husband but the Major gives her what she's missing; their understanding is silent and instinctive.

Another refreshing element of Ryan's Daughter is the portrayal of the English and the Irish. All too often in any film set in Ireland, the locals are universally pure hearted while the English are universally loathsome. Here you have small-minded Irish peasants and English soldiers who are just doing their job. You also have an IRA that kills police officers in cold blood. Yeah, the film may be simplistic, but at least it doesn't have a sentimental, misty-eyed view of the common man and the Emerald Isle.

And how can I talk about Ryan's Daughter and not mention the storm sequence? It's quite a remarkable piece of film and again it features some breathtaking photography – there's one shot where the waves crashing against the cliff seem to be blown backwards and another where the spray is sucked upwards into the sky. Anyone with a pair of eyes should enjoy it.

However, as much as I love the film, I do think it splutters towards its conclusion. I certainly don't mind it being three hours long, but the film does seem to run out of ideas towards the end. But despite this, it was brave of Lean to give the film such an open ending. You really are left with more questions than answers as regards this couple and their future. But such is my fondness for the film that I end up caring what happens to the characters after the credits roll. I want to know whether they make a go of things. And when that happens you know you're watching something special.

Directed by David Lean
Written by Robert Bolt
Produced by Anthony Havelock-Allan
Original Music by Maurice Jarre
Cinematography by Freddie Young
Starring Sarah Miles, Robert Mitchum, Trevor Howard, Christopher Jones and John Mills

Running Time: 206 mins

Rated R for boobies and twinkling, doomed orgasms