It is set in England in the late 15th century, and follows the exploits of the fictitious Prince Edmund as he is invested as Archbishop of Canterbury amid a Machiavellian plot by the King to acquire lands from the Catholic Church.

Edmund, faced with the threat of assassination, attempts to escape to France into self-imposed exile; and in a later scene, two drunk knights overhear King Richard IV exclaiming "Who will rid me of this turbulent priest?

Edmund attempts to flee to France with Baldrick and Percy, but is caught trying to escape by King Richard and Prince Harry, and claims he was going to Canterbury.

He proposes a new product line of holy relics including a set of Shrouds from Turin, a range of anachronistic gifts (such as a pipe racks or a coffee table) purportedly from the carpentry workshop of Jesus Christ, along with a variety of bones and other bodily parts of saints – all revealed to be counterfeit items produced by Baldrick himself.

Despite his initial displeasure, Edmund starts to settle in as archbishop, given the benefits the position brings him: he is gaining great new wealth for himself and the crown, for the first time his father actually respects him, and even without needing to kill his brother he has already become a politically powerful man in his own right.

Edmund is promptly excommunicated by the pope (and also two other antipopes), and walks away into a bright, holy light – revealed to be the glow from the fire he set in the nunnery.

In the epilogue, the Mother Superior laments the corruption of the world, and suggestively informs another nun that she won't be needing "the unicorn" that evening – the true nature of which is not revealed.

William Russell, best remembered as Doctor Who companion Ian Chesterton, was a last-minute replacement for actor Wilfrid Brambell in the role of the Duke of Winchester.

Also cut from the programme was a valedictory soliloquy by Edmund as he prepares to go into exile, bidding farewell to the castle turrets,[5] and King Richard preaching an angry sermon from the pulpit at the funeral of the dead Archbishop Godfrey.

While The Black Adder satirises the supposedly unquestioning credulity of the Mediaeval Christian, Lewis suggests that Chaucer's story, by offering a satirical commentary on the relic trade, shows that the teachings of the Church were open to question and ridicule even in the 14th century.