It might seem hard to believe now, but there was a time when there was no such a thing as Star Wars.

The epic money-generating space fantasy has been part of popular culture for so long that it’s sometimes hard to imagine that, a mere 40 years ago, no one had ever heard of Darth Vader. That all changed on 25 May 1977 when, before the days of spoilers and social media campaigns, writer-director George Lucas released his third feature film to a blissfully unaware public.

"It was simply a one hundred and twenty-one minute film called Star Wars. There was no Episode IV. There was no A New Hope. There was no franchise and… pretty much no expectations."

Harvey O’Brien joined Seán Rocks on Arena to mark the 40th anniversary of the release of George Lucas’s original Star Wars film, featuring the unknown lead trio of Mark Hamill, Harrison Ford and Carrie Fisher. Hamill plays Luke Skywalker, whose story, Harvey tells Seán, is "your classic quest: find a mystic talisman, defeat evil, assemble a team. That kind of thing." Luke’s story intersects with that of Princess Leia – via Obi-Wan Kenobi and Han Solo – and before you know if, you have the basis for a forty-year blockbuster franchise of eight films (and counting).

"The legacy of Star Wars is so massive that we take for granted the fact that everything was done on the fly when making that film."

Star Wars was a relatively low-budget film that Lucas wanted to look and sound unlike anything anyone had seen or heard before. Many of the visual and sound effects were created from scratch by the production team, to achieve Lucas’s vision of what Harvey says was – for his generation – a film that was "different, but the same".

What about the sequels? When did it become clear that Star Wars was not going to be a stand-alone film? Well, that happened pretty quickly, Harvey says, as the adventures of Luke Skywalker rapidly overtook those of Bruce and Brody in Jaws to become the biggest film of all time. The title A New Hope was only added on re-issues of the film, after the success of the sequel, The Empire Strikes Back. And so forty years of adventures from a galaxy far, far away began.

You can listen back to the full interview below: