Eddie Redmayne didn't know there would be five 'Fantastic Beasts and Where to Find Them' movies.

The Oscar-winning actor plays magizoologist Newt Scamander in the upcoming first installment of J.K. Rowling's series, and he admitted the recent announcement the planned trilogy is being extended by an additional two films came as a ''complete shock'' to the cast.

He said: ''She always had a specific story she wanted to tell, which goes much further beyond just Newt and his case.

''But we didn't realise it was going to be five films.''

Plot details for the saga have been kept tightly under wraps so Eddie can't wait for the movie's release in a few weeks time because he's found it ''really stressful'' not being able to speak out about the story.

He told talk show host Ellen DeGeneres: ''I'm useless at keeping secrets, so it's been a really stressful few months.

''But there are some great surprises--wonderful surprises that I'm very excited about.''

The 34-year-old star was in awe when he first read the script because of the level of detail used by the 'Harry Potter' author.

He explained: ''When I read the script, I had no idea what to expect. It blew my mind.

''The amazing thing about J.K. Rowling is oftentimes when you read scripts, it's just the dialogue that you see. But when you read her script, it was like reading one of her books.

''The intricacy of the detail, it was like you were taken back to all those things that you kind of love in Potter films, but now in the world of New York in the jazz age, prohibition [era].''

Though he can't talk about the specifics of the movie, Eddie was able to give a vague outline.

He said: ''It's set in J.K. Rowling's wizarding world. It's set 70 years before Harry Potter, and it's about this English magizooligist who arrives in New York with a case full of these extraordinary magical creatures, and a couple get out.

''That kind of sets in motion a whole chain of events.''