LONDON — Michael Gambon, who was Professor Albus Dumbledore in the Harry Potter movies, is to play Winston Churchill in ITV and Masterpiece’s feature-length film “Churchill’s Secret.” Lindsay Duncan co-stars as Clementine Churchill.

Set during the summer months of 1953, Churchill — now British Prime Minister for the second time and in his late 70s — suffers a life-threatening stroke, which is kept secret from the world. Told from the viewpoint of his young nurse, Millie Appleyard, the drama follows his battle to recover as his long-suffering wife, Clemmie, desperately hopes the stroke will force Winston to retire, while his political friends and foes plot to determine who will succeed him. Meanwhile, his adult children descend on his home, Chartwell, unsure if he will pull through, as tensions within his family begin to surface.

Filming will begin next month in London, and at Chartwell in Kent. The film will air in the U.S. on PBS in 2016.

Rebecca Eaton, executive producer for Masterpiece, said: “Winston Churchill is an epic figure to Americans, much as he is to the British. He epitomizes the Special Relationship, a phrase he coined.”

The drama will be adapted by Stewart Harcourt from Jonathan Smith’s book “The Churchill Secret: KBO.” It will be directed “Da Vinci’s Demons’” Charles Sturridge, with Timothy Bricknell producing.

“Churchill’s Secret” is a Daybreak Pictures-Masterpiece co-production for ITV. Passion Distribution will handle international sales. Executive producers Hal Vogel and David Aukin will oversee production.