The actor, 50, was spotted riding around Rome on a scooter with his Pursuit of Love co-star James, 31, earlier this week.
Other photos obtained by the Daily Mail appeared to show West and James kissing at a restaurant in the Italian capital.
After returning home to the UK, West and his wife made a joint appearance outside their home in Wiltshire, smiling and kissing for the cameras.
They also shared a handwritten note with the press, which was reportedly left outside their gate.
“Our marriage is strong and we are very much still together,” it read, followed by the couple’s signatures.
West, best known for his roles in US dramas like The Wire and The Affair, married landscape designer FitzGerald, 49, in 2010.
The couple share four children, Dora, 13, Senan, 10, Francis, nine, and Christabel, five. West also has a 22-year-old daughter from a previous relationship.
Recent reports suggested that the couple had “crisis talks” following West’s return from Italy, with sources close to FitzGerald claimed she had been left “lost for words” by the photos.
“Catherine has seen the photos and she’s devastated,” a friend told MailOnline, adding: “She’s totally shocked because she didn’t know anything was going on.
“They were very much together, so this is completely out of the blue.”
West and James recently worked together on the BBC’s upcoming adaptation of Nancy Mitford’s The Pursuit Of Love, which also stars Emily Mortimer and Andrew Scott.
They previously starred alongside each other in the 2011 production of Othello at the Crucible in Sheffield.
James, who is thought to have split from Doctor Who actor Matt Smith earlier this year, is yet to comment on the photos.