Colin Farrell in 2019. Photo / Getty Images

Irish actor Colin Farrell is barely recognisable in his latest TV role.

The 45-year-old Golden Globe winner has revealed he had to pack on the kilos for BBC Two's period drama, The North Water, which hits streaming on Foxtel today.

Based on Ian McGuire's best-selling novel of the same name, the five-part series tells the story of Patrick Sumner (Jack O'Connell), a disgraced ex-army surgeon who signs up as ship's doctor on a whaling expedition to the Arctic. On board, he crosses paths with brutish killer Henry Drax (Farrell), the harpooner.

A usually clean-cut Farrell sports an unkempt beard and longer hair to transform into his disturbing character.

"I did get fairly strong," Farrell said at a press event.

"Look, I just put on weight. I just lifted weights and ate, and that's all. Anyone could do it really, although I wouldn't advise it.

"You couldn't take off the costume. I couldn't really step away from the character. I couldn't get out of the costume, he was always with me.

"It was a great benefit to me because it just meant 24 hours a day, seven days a week for however many weeks we shot, I was constantly inhabiting this physical space that was very different for me."

Farrell added: "He was a fairly explicitly described character physically [in the book]. There was a certain kind of power to his body – the way he filled space, the way he moves through space – and a certain brute strength that he had, and the confidence of a man that carries himself with a keen awareness of that brute strength."

The series also stars Stephen Graham (Line of Duty, The Irishman), Tom Courtenay (45 Years, The Aeronauts) and Peter Mullan (Mum, Top Of The Lake).

Foxtel said in a press release that the cast and production team, which filmed primarily in the Arctic, sailed as far as 81 degrees north, the "furthest point north it is believed a drama series has ever filmed before".

It is just the latest in a string of dramatic onscreen transformations for Farrell, who stunned fans when he was revealed as Penguin in the first The Batman trailer last year.

I had to search the eyes to confirm this is, in fact, my man Colin Farrell. #TheBatman #DCFanDome

— Jamie Jirak (@JamieCinematics) August 23, 2020

Farrell was seen sporting significant weight gain and wearing heavy prosthetics on his face to portray the iconic villain, Oswald "The Penguin" Cobblepot.

The movie, starring Robert Pattinson as the caped crusader, began filming early last year but has suffered a series of setbacks due to the Covid-19 pandemic.

It's scheduled for a March 2022 release.