Lily James reveals the tough workout routine that helped her transform into Pamela Anderson

Lily James has revealed the intense workout routine a personal trainer put her through— in order to play the Baywatch star for her latest role.

Fans of Lily James were amazed at her shocking Pamela Anderson transformation for a new Hulu show Pammy & Tommy. The series, which airs next month and also stars Sebastian Stan as Tommy Lee, follows the couple as their honeymoon sex tape is leaked on the Internet.

In order to transform into the star, Lily explained that a celebrity trainer put her through her paces, making her do intense boxing classes and running—while she was reading the scripts.

The Downton actress, who spoke about the Dominic West affair scandal last year, told Entertainment Weekly,  "I worked with this amazing trainer, Matt Bevan, who worked with Daisy Ridley as well. He worked me so hard and I got really fit. I lost a tonne of weight. I’ve put it all back on again though, unfortunately. But I felt really athletic, which I hadn’t done for a long time and there was great confidence that came from that."

Whether you love running on the treadmill or outside, Lily seems to be great at multi-tasking when she's in the gym, and admitted, “He would make me do all my work and reading my script on a running machine."

While there was one part of her workout routine she loved, "I did boxing with a really cool guy in LA, which I love too, being physically strong like I could literally beat someone up."

Lily, who also appeared in the Netflix adaption of Rebecca, admitted that her fitness routine wasn't the only thing she had to work—every day she was on set she had to sit in the make up chair for 4 hours.

She explained, “We explored tons of different prosthetics like nose, chin, eyebrows, forehead, but in the end we stripped it back as much as possible.  We didn’t want there to be too much of a barrier between me and my expressions.”

While it was the breast prosthetics that were the biggest change for her - with the actress revealing that she loved them, but they were uncomfortable to wear and got 'sweaty'.