It started in the middle of the story and then the first three episodes were made. But, as director George Lucas wraps up the Star Wars saga, Steve Pratt reveals the Force may still be with us.

Earlier this year, the cameras rolled as actor Hayden Christensen ran frantically across a platform on a sound stage at Elstree Studios in Borehamwood, on the outskirts of London. Not, you may think, a particularly significant moment in the history of film-making - until you hear that this action was followed by bearded American man quietly proclaiming, "Cut, that's a wrap".

Writer and director George Lucas's comment indicated this was the last time cameras would roll on a Star Wars movie. In a neat touch, it happened on Stage 8, the same place where the American film-maker committed the first soundstage shot to film on Episode IV: A New Hope in 1976.

"It completed the circle. George was really happy about that," says producer Rick McCallum.

Lucas's four little words indicated the end of a screen series that changed the face of Hollywood film-making, marketing and merchandising. The original Star Wars and Jaws, made by friend Steven Spielberg two years previously, heralded the arrival of the blockbuster movie as well as pushing the profitable summer season forward to May.

Even starting in the middle of the story failed to deter audiences. Lucas filmed Episodes IV, V and VI before, after a 15-year gap, bringing the first three episodes to the screen. Whether he did this because he felt they were the only ones he could make with the available technology or because he wanted to emulate the cliff-hanging tradition of Saturday morning serials doesn't matter. The film worked.

Characters and phrases from the series have worked their way into not only the public imagination but also the language, with both "Jedi" and "the dark side" listed in the Oxford English Dictionary.

Lucas and the films didn't just entertain audiences, they inspired a whole host of film-makers. "Star Wars smashed open the possibilities of what film could actually do," says Peter Jackson, Oscar-winning director of The Lord Of The Rings trilogy. "It was the perfect film to inspire a sense of wonder".

This wasn't the view of the Hollywood studios who turned down Star Wars. Twentieth Century Fox eventually backed the first film but, clearly doubting its ability to succeed, handed the sequel and merchandising rights to Lucas in return for reducing his fee on what they viewed as a risky undertaking.

Undoubtedly, they regret that decision. The series has made him a millionaire with his own company, Lucasfilm, and Industrial Light and Magic, the company he created to achieve the visual effects. His entertainment empire generates more than a $1bn in revenue each year.

The Star Wars spin-offs have revolutionised both movie-making and film-going, from the introduction of improved sound systems to experiments in computer-generated animation made possible by the profits from Star Wars. They resulted in the creation of the Pixar computer, which led to the formation of the company behind such movies as Toy Story and Finding Nemo.

Lucas has never been one to rest on his laurels. When he decided to complete the story by filming the first three chapters, he pioneered using digital motion picture production techniques.

Attack Of The Clones - Episode I - was the first major feature created using a high definition digital video camera and videotape. This was developed further to create a new technology called "444" for the latest film, Revenge Of The Sith. How different to making the first Star Wars with droids that wouldn't function and aliens that someone claimed looked like Beatrix Potter rejects.

It made a star of Harrison Ford, whose intergalactic adventurer Han Solo was a throwback to early serial heroes. He went on to help Lucas and Spielberg create another cinematic icon, Indiana Jones. Strange to think that the leading actor of Revenge Of The Sith, Hayden Christensen, wasn't even born when the first Star Wars was released.

Lucas hasn't won the Star Wars without criticism. The moans from both critics and fans that greeted Episodes I and II, The Phantom Menace and Attack Of The Clones, were loud and clear. They echoed those that greeted the first episode, dismissed by one reviewer as "heartless fireworks ignited by a permanently retarded director with too much clout and cash".

Perhaps that missed the point. Lucas was adamant that he was making a film for a generation that had grown up without fairy tales. He wanted to recapture the excitement and fast pace of the Saturday serials that he loved as a child. It's a format that he carried through to the end, with Revenge Of The Sith being 140 minutes of virtually non-stop space battles and lightsabre fights as the complicated family history of Anakin Skywalker unravels to its Darth Vader conclusion.

This is a world where good and evil are clearly defined and turning to the dark side has nothing to do with saving on electricity bills.

Names such as Wookies, Jabba the Hutt and Darth Maul might seem ridiculous to some. Occasional characters - step forward Jar Jar Binks and Ewoks - test the patience. And you can't help but laugh at Princess Leia's currant bun hairstyle. But audiences are always ready for a large dollop of sheer escapism.

Seeing all the pieces fall into place on Revenge Of The Sith leaves 61-year-old Lucas with a sense of satisfaction as well as the need to find something else to fill his days. "A lot of my life has been wrapped up in this one thing. I can walk away from this now because I feel it's the best I could do. I'm happy with it," he says.

Not that Sith will be the end of Star Wars, although he denies that he ever envisaged a final trilogy. But the story will continue on TV, with plans for a 3D animated series and live action series featuring characters from the saga.

Without a doubt, The Force is going to be with us for a long time to come.

* Star Wars Episode III: Revenge Of The Sith (12A) goes on general release on Thursday, after late night previews in some cinemas on Wednesday.