Adam Driver found it "exhausting" trying to "mirror" a horse's "physicality" for the Burberry Hero campaign.

The 'House of Gucci' star - who recently admitted he "needs" to exercise for his "sanity" - started to question what he was doing when he suggested the idea to director Jonathan Glazer for the promo he shot for the iconic British fashion house's scent.

The minute-long clip released earlier this year sees the 'Star Wars: The Force Awakens' actor running into the sea trying to keep up with a stallion, before swimming in the ocean and riding the animal - all while topless.

And he quipped: “I had a conversation with Jonathan about the images and this idea of mirroring a horse’s physicality which, in my face, is fine. But in my body seemed really ambitious."

The 'Girls' star continued: “I started training pretty soon after that, to get in shape and to try to be as sinewy as a horse, which is exhausting and interesting, and definitely peppered with moments of ‘what the hell am I doing?’”

The 38-year-old star admitted it was pretty "nerve-wracking" working in such close proximity to a horse and he doesn't want to do it again.

He added to AnOther Magazine: “They’re big and they’re primadonnas.

"It’s nerve-racking when you’re treading water in the ocean and they pull this horse out, and he turns around and just stares you down with his mouth open. Having to [swim with him], latch on and ride him to shore is definitely something I don’t think I’ll repeat in my life.”