"I ate a lot of chicken and lifted heavy things," Mescal said on “The Graham Norton Show”, reports people.com.

While preparing to play the former-royal, who was forced into slavery, the Kildare, Ireland, native worked "with a trainer who circled me like a shark and said, ‘There is a canvas to work with.' "

Mescal got so muscular that his co-star Pedro Pascal gave him a nickname.

"I call him Brick Wall Paul... He got so strong. I would rather be thrown from a building than have to fight him again," Pascal told Vanity Fair in July.

Mescal told Norton his trainer "went to town, and I saw him every day. It was fun."

However, Mescal said to have some caveats when it came to his fitness regimen.

"I did everything he asked, but I like to drink, and I like to smoke, so I drew a line in the sand where those were concerned."

Mescal flaunted his abs in the trailer for the film, where he fights a rhino, among others, in the famed Roman Colosseum.

But another of Norton's guests disagreed with Mescal’s assessment of working out being “fun” – Eddie Redmayne, who recently underwent his own physical transformation, getting shredded to play an assassin in the series “Day of the Jackal”.

“I profoundly disagree with Paul – it was not fun, it was horrendous,” said the actor.

"You read a scene in the script that says, ‘He is topless, sinuous and ripped,' and you think, 'Oh, here comes the chicken diet.' "

Saoirse Ronan and Denzel Washington, who also stars in Gladiator II, appeared on the episode as well. Mescal said that he was intimidated meeting the legendary Washington, 69.

"It was a big day in my life – it was amazing. I spent the first day thinking, 'I must go introduce myself to him' and I stood there for several minutes before I decide, 'Not today.' The next day I decided to be a brave boy!"