Stiles was in London at a promotion event of her new series “Riviera”, set to premiere on June 15.
The mother-to-be clad in a black fitted dress which she paired with a red trench coat and green pumps.
Nick Snaith, who interviewed Stiles, took to Twitter to share a photograph of him with the “Jason Bourne” actress.
In the image, Stiles can be seen heartly touching her baby bump as she posed for the camera.
Later, Stiles’s representative confirmed that she is currently pregnant. She and Preston will welcome their child later this year.