Written by Richard Carpenter, the show ran for three series between 1984 and 1986.
Now, in tribute to Carpenter - who died in 2012 - "The Knights of the Apocalypse" will be recorded and aired in early 2016, with all proceeds going to charity, reported Digital Spy.
Carpenter wrote the episode following the end of the TV series, and nothing was ever done with it until now.
The new installment sees the return of original cast members including Ray Winstone, Jason Connery, Clive Mantle, Judi Trott and Nikolas Grace.
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"The Hooded Man is ready to face the evil machinations of the Sheriff of Nottingham again, surrounded by my wonderful band of Merries, in a brand-new audio adventure written by Kip himself. We may be a little older and wiser in real life but, on audio, we're forever young and golden-haired."
"The Knights of the Apocalypse" comes from Bafflegab Productions, and will air in early 2016.