The trans comedian plays the dual role in a new interpretation of Robert Louis Stevenson's classic novella, starring opposite Scott Chambers' Robert. It follows Chambers' character as he comes into the employment of Nina Jekyll only to become embroiled in a dark plot hatched by her machiavellian alter-ego.
"When Rachel finally arrives I didn't quite expect it to be like that, but I wasn't really controlling it. I've latched to myself and I just found her out there and she's quite odd," Izzard says of transforming into Hyde on set.
"I remember I was looking out and looking at people, and they were looking at me strangely because I really let go and she happened out there in the scene in real time."Eddie Izzard
The film, Izzard says, was filmed so that Rachel's big moment —which appears towards the end of the film— came later on in the process, something that was beneficial to the comedian's performance.
"There was a lot of of my character work, my characters work, that was kind of in time and the ending of our film we shot towards the end of our shoot," Izzard explains.
"Which was really helpful for me. I wanted to land Nina first, and then build Rachel out of there, and Rachel had to be different to Nina. So I needed to ground Nina first."
Rather than look back at other interpretations of the character, Izzard decided to go back to the source and relied upon Robert Louis Stevenson's book to inform her take.
"I didn't want to see any performances before of what anyone else did, I probably have seen one or two when I was a teenager, probably Hammer versions," she admits.
"But the novella was my key thing to read, Robert Louis Stevenson wrote in the late 1800s and it's a novella as opposed to a novel, so it's quite short and it leaves a lot to your own imagination.
"It gives you the chance to go the way you will, and with the story that Joe was already bringing to me to play I could ground myself in that and then let Rachel come off that."Eddie Izzard
Bringing Hammer Horror back from the dead
Doctor Jekyll is pitched as being the film to give Hammer films the energy it needs to be revived after losing momentum following decades of dominating the horror genre with its classic Hammer Horror films like Dracula, Frankenstein, and the Mummy.
But even with the weight of this notion, director Joe Stephenson admits he "didn't feel any pressure" at the time of filming.
"It's so busy when you're making a film, you just have so many things going on in your head and you just can't think about those sorts of things at that point."Joe Stephenson
"I think the pressure came afterwards, actually, I think it was after the shoot and I realised 'oh gosh'."
Izzard adds, "Hammer did come to join us, because there was early rumblings of Hammer coming in. I think [Joe] mentioned to me [that] there were people from Hammer who, because Hammer was trying to get back on its feet, were coming onto the set and go 'oh right.'
"But that was towards the end of the film, so from my perspective it didn't matter to me because I think we needed to make our film, and if Hammer wishes to come and join us that was great."
Hammer films was bought by John Gore in 2023, and Izzard says of the CEO's vision: "John Gore has taken over Hammer and he's a very determined person, very ambitious for Hammer to go forward.
"So that was just a great thing that could happen and suddenly we're doing this big opening, we're opening for Halloween, and I think it's a perfect thing for a lot of people to go see."
She goes on: "We have an attention to detail, we have quality and great acting... it was a great role for me to go for and if this works with Hammer, I think it's just a nice pairing."
Stephenson called Hammer films interest in Doctor Jekyll a fortuitous moment.
"It feels like a perfect marriage, we basically made the film that we wanted to make and it's just a perfect marriage that's kind of happened here."Joe Stephenson
"It felt like we were already leaning into lots of things that Hammer are are all about and and you know it's lovely. But I suppose the pressure is really on the release, it wasn't on the making of the film."
Doctor Jekyll will be released exclusively in UK cinemas on Friday, 27 October.
Watch the trailer for Doctor Jekyll: