One glance at Lily James and Dominic West's Roman holiday and you'll be saying "Mamma Mia!"
Paparazzi captured numerous photos of The Pursuit of Love stars in a heated embrace, one of which shows Dominic kissing Lily's neck.
An eyewitness tells E! News that Dominic, who is married to Catherine FitzGerald, engaged in plenty of PDA with his co-star during a lunch with their friend and manager, Angharad Wood. "At the end of lunch Lily sat next to Dominic and he couldn't resist kissing her neck and stroking her," the source describes. "They then visited the nearby church and Dominic placed his hand on Lily's butt."
Prior to their rendezvous with Angharad, Lily, 31, and Dominic, 50, did a bit of sightseeing around the Spanish Steps and Piazza di Pietra, according to the insider. And if their weekend getaway wasn't romantic enough, the eyewitness says Lily and Dominic rode around Rome on an electric scooter, à la Lizzie and Paolo in The Lizzie McGuire Movie.
The insider adds that the pair spent the rest of the evening at the centrally-located Hotel de la Ville, where they stayed in a suite with a panoramic view for their two-night trip.
And when it came to their goodbye, the source describes a tender farewell, sharing how the two actors shared a long embrace and many kisses before parting.
Neither of the celebrities have commented on their apparent romance.
Lily and Dominic are currently working together on the set of the period drama The Pursuit of Love. The Cinderella star is playing the lead role of Linda Radlett, but it's unclear if Dominic plays one of Linda's three suitors.
Additionally, it's unknown if Dominic and his wife, Catherine, have split, as neither have commented on their relationship status.
According to the Irish Examiner, Dominic and Catherine dated for three years while attending Trinity College in the early '90s, and rekindled their relationship in 2002. They went on to have three children, Dora, 14, Senan, 12, and Francis, 11, before getting married in 2010. Dominic also has daughter, Martha West, whom he welcomed during a previous relationship.
For her part, Lily was last linked to Captain America star Chris Evans. The two had fans thinking they were dating when Chris spent a week with the Brit in her hometown of London, where they were spotted eating ice cream in a park and enjoying a night out on the town.
And prior to her speculated summer romance with Chris, she was dating Pride & Prejudice & Zombies co-star Matt Smith. They had been together off-and-on for nearly five years, but The Daily Mail reports that the duo officially called it quits on their relationship as recently as last week.
E! News has reached out to Lily and Dominic's reps for comment.