The co-creator of Back To The Future has said the film would have never been the success it was if Eric Stoltz had not been replaced by Michael J Fox as Marty McFly while the film was already in production.

The Pulp Fiction actor was originally cast in the 1985 classic movie about a high school student who is accidentally sent 30 years into the past in a time-travelling DeLorean, but was dropped after a month of filming.

Writer Bob Gale, who penned the script with director Robert Zemeckis after discovering his own father’s high school yearbook, told the PA news agency: “If we had finished the film with Eric Stoltz I don’t think we would be having this conversation today, Michael was that much better.

“He was so perfect, you can’t imagine anyone else to be him, although when you see Back To The Future The Musical in London when we open in May or June, you will see Olly Dobson playing Marty McFly and you will say ‘Wow this kid is great, I totally accept him as Marty’, so it can be done and we have done it, but Michael J Fox was perfect, it’s hard to imagine anybody else as Marty.

“It’s hard to imagine anybody else in any of those key roles really, they grew into their parts thanks to their own talent, thanks to Bob Zemeckis’s directing, thanks to what was a pretty good script, and everything else that was in support of the picture.”

Michael J Fox with Lea Thompson in Back To The Future (Universal Home Entertainment)

The film is now 35 years old but Gale said: “So much of it is extremely vivid, it is in a weird way kind of like watching a home movie.”

However, the writer said it would be unlikely the film, which is based on an original idea rather than a pre-existing property, would be made in 2020.

He said: “I think we would have a very hard time getting it made because it’s really hard to get something original made and then in today’s environment they would say what is this relationship between Marty and Doc? ‘Is there some paedophilia thing happening here?’ People would say that today.

Fox with Christopher Lloyd as Doc (Universal Home Entertainment)

“Watch the movie and it never crosses your mind, you just say ‘Oh Marty is fascinated by this guy, he’s the father that Marty didn’t have, Doc hired this guy as his helper cos they are both kind of outcasts’ and we see it play out and you just totally buy it.

“But in today’s world studio executives would completely overthink it and I don’t know what kind of movie it would turn out to be if we were trying to make it today but I’m just really glad that it was made when we did.”

Back To The Future: The Ultimate Trilogy is available for the first time on 4K on October 19 from Universal Home Entertainment.