The mysterious, hidden-away little brother of two English kings, who was also uncle of the current queen, is the subject of a powerful drama by award-winning playwright Stephen Poliakoff, on “The Lost Prince,” airing on Masterpiece Theatre Sundays, Oct. 17-24, 9-11 p.m. EDT (check local listings). One of the most acclaimed dramas ever to air in the UK, “The Lost Prince” is the premiere of Masterpiece Theatre’s 34th season.

“The Lost Prince” charts the little-known tale of Prince John, the youngest child of George V and Queen Mary. John’s short life encompassed one of the greatest periods of upheaval in history: the complex build-up to the First World War and the political traumas that beset the European monarchies at the beginning of the 20th century. Many of the scenes have a particular power in today’s politically charged atmosphere.

Set against a backdrop of enormous political change, “The Lost Prince” recounts the human story of a remarkable boy struggling to grow up in a unique and sometimes bizarre family. Suffering from epilepsy and learning difficulties akin to autism, Johnnie was excluded from public life and forced to lead an increasingly isolated life. However, he drew strength from the unfailing support of his devoted nanny, Lalla.

“His short life started at the height of the imperial splendor of the British Empire, and when he died the whole of that had been ripped apart by the First World War,” says writer-director Poliakoff. “It was an extraordinary dramatic arc — this little boy who was forgotten while the world around him completely lost control.”

During its British broadcast, “The Lost Prince” created a sensation for its revelations about the young prince and his dysfunctional royal family.

Matthew Thomas stars as the teenage Prince John, with Daniel Williams as the younger Johnnie. Gina McKee (“The Forsyte Saga”) stars as his devoted nanny, Lalla, who conceals the frequency of the boy’s seizures from his parents. When they become aware of his condition, they exile Johnnie and Lalla to a secluded cottage, preventing embarrassment to the royal family.

The remarkable cast also includes Miranda Richardson (“The Hours”) as Queen Mary; Tom Hollander (“Gosford Park”) as George V; Michael Gambon (“Harry Potter and the Prisoner of Azkaban,” “Gosford Park”) as Johnnie’s grandfather, Edward VII; and Bibi Andersson (“The Seventh Seal”) as his doting grandmother, Queen Alexandra.

Also featured are Bill Nighy (“Love, Actually”) as Lord Stamfordham, confidant to the king and the young princes; and Frank Finlay (“The Pianist”) as Prime Minister Asquith, who easily intimidates everyone except Johnnie.

Poliakoff was inspired to make the film when he saw a haunting photograph of Prince John in a British newspaper. At first unable to learn more than a few snippets of information about the boy, he gradually assembled a compelling portrait of a funny, fascinating and misunderstood kid.

“It was a chance to celebrate a child with disability,” said Poliakoff, “to show him not as a victim but as somebody who does progress, does achieve a kind of equilibrium at the end of the story so that everybody notices him; and he’s able to do it on an epic scale.”

Producer John Chapman emphasizes that Johnnie has a lucid, yet detached stance on these world-shattering events going on around him. “This is a celebration of apartness,” he asserts. “Johnnie has learning difficulties, and he has a very unusual view of the world. He sees things clearly but differently. He is like the boy who is clear-sighted enough to say, ‘The Emperor has no clothes!’ The script bristles with his insights.”

It’s a story that is able to reach out to all ages and all classes, Chapman stressed. “You can’t say, ‘Oh, it’s just another period drama,’ because its perspective is so individual. It’s a highly original piece of work, which simply socks you in the jaw.”