ACTOR Dominic West was seen passionately kissing younger co-star Lily James on a busy flight.
Pictures in The Sun of them cuddling during lunch in the Italian capital have already caused a sensation.
And a shocked witness on the BA trip said: “I recognised him instantly but wasn’t sure who she was.
“At first, I thought she was his daughter, as I knew he was around 50 and you could tell she was a lot younger.
“Within minutes of the plane leaving, they began kissing and cuddling after both removed their masks.
“They looked like a couple heading for a dirty weekend and they were all over each other. They were French kissing and there was a lot of necking going on.”
West, who found fame in hit series The Wire, and ex-Downton Abbey star Lily have been filming a BBC adaptation of The Pursuit Of Love.
After the cosy lunch photos emerged earlier this week, smirking West posed for photos with wife Catherine Fitzgerald, 49, outside their country mansion on Tuesday morning as the couple insisted their marriage was as strong as ever.
The businessman who saw him with Lily on the flight added: “I didn’t know who she was until I saw the story in the paper about him and her in Rome.
“To be honest, the reason I’m speaking out is because of that cringing statement and photocall he and his wife gave.
“When they were on the plane they behaved very much like a couple. He was whispering passionately in her ear while they kissed.”
The pair were also seen heading back to the airport together after the three-night stay.