Aidan Turner and Eleanor Tomlinson race horses on the "Poldark" set.
The pair - who play Ross and Demelza Poldark in the BBC One show - often have to ride equines on the programme, and when the cameras are not rolling he loves to see how quickly his four-legged friend Seamus can go against Eleanor's horse.
He said: "We race quite often and we're very competitive. Eleanor wins all the time, she has a better horse - it's just a faster horse.
"And she's a very experienced rider. Also she can beat me while being slightly hampered because she rides in a side-saddle and it's really hard to gallop with that.
"Seamus isn't happy about losing either."
However, Aidan could soon be beating Eleanor in the races because Seamus may have to be put out to pasture, much to the 34-year-old actor's disappointment.
He added to the Daily Star newspaper: "There was talk of my on-screen horse Seamus needing to retire as he is 17 now.
"I love Seamus, he's a real star and I have a huge attachment to him, but if he needs to retire..."
Aidan and Eleanor are to star in Poldark's fourth series shortly, which will see villain Monk Adderley (Max Bennett) cause chaos for Ross and Demelza.
Writer Debbie Horsfield said: "We have one character who is a real rogue and goes head to head with Ross.
"I suspect the Monk storyline is one that the audience will particularly relish."
Aidan added to the Daily Mirror newspaper: "He's a creep."
Last month, the actor hinted "Poldark" could come to an end next year.
Aidan said: "I think next year might be the last one, certainly for a while. There's a huge gap in the books, about 15 years."