Most film buffs know that Eric Stoltz was the original Marty McFly in Back to the Future before director Robert Zemeckis made the difficult decision to replace him with Michael J Fox.

Stoltz had already shot for five weeks as Marty when he was let go from the production, and now a new behind-the-scenes book - We Don't Need Roads: The Making of the Back to the Future Trilogy by Caseen Gaines - has shed fresh light on the dismissal.

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According to accounts from cast and crew on the movie, Stoltz approached Marty in a "method" acting style and lacked the comedic lightness of touch Zemeckis and his co-writer/co-producer Bob Gale wanted for the part.

In We Don't Need Roads (via Vulture), Gale recalled how Stoltz insisted on being referred to as "Marty" even when cameras stopped rolling.

"We almost always called him Marty," he said. "We thought it was silly, but we figured if it helped him do his job, it was harmless. There were a few people on the crew who'd worked on Mask and they called him Rocky, the name of his character in that film."

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Christopher Lloyd added of Stoltz's take on the time-travelling teen: "I felt for Eric. He was a really good actor. Although he was doing the part well, he was not bringing that element of comedy to the screen."

Lea Thompson, who had worked with Stoltz on 1984 film The Wild Life, said that she initially took news of her co-star's firing hard.

"It was hard for me because I was really good friends with Eric," she said "Eric is such a different actor and he could be very difficult...

"[He] had such an intensity. He saw drama in things. He wasn't really a comedian, and they needed a comedian. He's super-funny in real life, but he didn't approach his work like that, and they really needed somebody who had those chops."

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Stoltz also reportedly clashed with Thomas F Wilson on set, bruising the Biff Tannen actor's collarbone after repeatedly pushing him hard during the '50s cafe scene.

After the decision was made to fire Stoltz, production actually continued in early January 1985 with the actor working alongside Lloyd to film the Twin Pines mall scene.

Director of photography Dean Cundey confessed that he felt an uneasiness on set in the final days.

"When we would set up a shot and we would shoot Chris Lloyd's angle, but we wouldn't do the reverse on Marty," he said. "I'd say, 'Don't we need the angle?' and Bob would say, 'No, no, no, let's not worry about that'. It didn't take long for me to see that we were saving our energy for what would come next."

Back to the Future turns 30 this week! Here's how the film could've looked with Eric Stoltz as Marty McFly pic.twitter.com/XHrz2dBWyc â€” Digital Spy Film (@digitalspyfilm) June 29, 2015

Zemeckis and producers Gale, Neil Canton, Kathleen Kennedy, Frank Marshall and Steven Spielberg were all present when the announcement was made to crew that Stoltz was being released.

By that point, studio Universal Pictures had already negotiated around Fox's Family Ties schedule and the actor swiftly began filming the Twin Pines mall sequence with Lloyd.

We Don't Need Roads: The Making of the Back to the Future Trilogy is available now in the US and Kindle Edition, and will debut in paperback in the UK on July 9.