Lily James on her unrecognisable Pamela Anderson transformation

Lily James looks completely different when in character as Pamela Anderson. Photo / Getty Images and Hulu

Lily James felt "liberated" playing Pamela Anderson.

The 32-year-old actress portrays the Baywatch star in new Hulu miniseries Pam & Tommy - which focuses on the 1995 leak of the then-couple's sex tape - and although she had to undergo a gruelling four-hour physical transformation before filming each day, she found it "freeing" to look so unlike herself.

She said, "And then, of course, there was the physical transformation. Slowly, our incredible team found a balance where I resembled Pamela but also felt like I could act through it.

"I've never done anything where I look very different from myself before. And I'd really like to continue in this vein because I felt there was something very freeing and liberating in it. There was a bravery that came from that. A courage that came from… disappearing."

Lily admitted she has "never worked so hard" as she did when researching the blonde beauty.

Lily James looks completely different when in character as Pamela Anderson. Photo / Getty Images and Hulu

She told PORTER magazine, "I've never worked so hard. I've read all the books [Anderson] has written, I read her poetry, I can parrot along to all her interviews."

And the Mamma Mia 2: Here We Go Again star admitted it was hard to shake off her character once filming was complete.

She said, "It takes a while to let a character like that leave you. In the past, I maybe felt too modest to believe that I might inhabit a role so greatly that it would impact on me, but it really does. My therapist said that when her husband watches a rugby match, by the end he's exhausted – your nervous system doesn't really know the difference, whether it's him winning a goal or watching it happen. And I think the same happens when you live through someone."

James' co-star, Sebastian Stan - who plays Tommy Lee- recently admitted he didn't recognise the actress when he saw her out of costume for the first time.

He said: "It's really wild, with Lily, because the first time I saw her as herself was actually at the end of the shoot five months later," he said, "and I was like, 'Who are you?' That's when we actually formally met."