Marc Warren "struggled" filming "Beecham House" because of pollution "concerns".
The 52-year-old star was worried about pollution levels while shooting the period drama - which is set in 1795 and has been dubbed "Delhi Downton" - in India, so he avoided doing much sightseeing.
Speaking to BANG Showbiz and other media, he said: "I struggled with India. I'd been before, I've been to Kerala. If you've never been to India there are no words that can describe it.
"Jaipur was a real experience.
"The thing I struggled with the most was the pollution. I don't know how much people are aware of that.
"If you look on your app on your phone it'll say London can have a pollution range of say one. And where we were it could range from 300 to 450.
"That was a bit of a concern, so I wasn't doing all the sightseeing."
But the "Mad Dogs" actor loved appearing alongside some "wonderful actors" on the show - which also stars Adil Ray, Pallavi Sharda, Bessie Carter, Dakota Blue Richards and Shriya Pilgaonkar - and has predicted some will become "big stars".
Marc - who plays Samuel Parker, the best friend of Tom Bateman's titular character John Beecham - added: "I was aware I was on a really fantastic production with really wonderful actors.
"Some of the actors were obviously going to become big stars, I could see that. They were so talented. That was unfolding before you."
"Beecham House" - which has been created by "Bend it Like Beckham" director Gurinder Chadha - will air on ITV this summer.
The programme tells the story of Englishman John who lives in a magnificent mansion, Beecham House, in Delhi.
He aims to be an honorable trader after resigning from military service when he was left appalled by the exploitation carried out by the British East India Company.