Game Of Thrones star Richard Dormer will lead the cast in a series inspired by the Discworld novels.
Sir Terry Pratchett's work is being adapted by the BBC Studios for new comedy-drama, The Watch.
Dormer, who played Beric Dondarrion in Game Of Thrones, will star in the new show set in Ankh-Morpork.
The eight-part series follows the law enforcement efforts in the crime-ridden fictional city.
Dormer said: "I'm so thrilled to be part of this brilliant madness and mayhem. I was immediately drawn to the multitude of layers to Sam Vimes, and I find the dynamic between him and his band of disenfranchised comrades very compelling."
The City Watch of Sir Terry's fictional city state was introduced first in Guards! Guards!, which outlined the bumbling heroism of the fantasy law enforcers, with Vimes leading the group.
Writer Simon Allen said: "Sir Terry Pratchett is in the bloodstream of popular culture.
"He has a distinctly British kind of literary heart and humour but his ideas are defiantly human and universal.
"The Watch is a hopeful show that believes it's better to light a candle than curse the darkness.
"I can't wait for everybody to see our joyously brilliant cast light candles and, of course, flamethrowers."
The Watch starts filming in South Africa on September 30.
