Arthur Wellesley, 1st Duke of Wellington is the main antagonist of the final episode of the third season of Blackadder and a minor character in Blackadder: Back and Fourth.
He was portrayed by Stephen Fry.
In the third season's final episode "Duel and Duality", after recieving news of George, Prince of Wales having a sexual encounter with his two nieces, Wellesley challenges the Prince Regent to a duel.
Baldrick, in a rare showing of intelligence, suggests Edmund Blackadder, Esq. and the Prince switch places. Baldrick elaborates that his cousin has informed most histroic figures of the time are "painted to a romantic ideal rather than the true depiction of the idiosyncratic facial qualities of the person in question." Since Wellesley has only seen the Prince Regent in paintings and never met him in-person, he wouldn't think twice if Blackadder were to take the Prince Regent's place.
When Wellesley arrives he gives the Prince Regent (Blackadder) a briefing on the current war with Napoleon; after the Prince Regent (Blackadder) gives him some very vital strategic military advice, Wellesley admits he was told the Prince Regent was a "confounded moron" (which was true) and now regrets he has to kill him, but will still do it.
When Blackadder (Prince Regent) arrives with Wellesley's tea, he sets the refreshments on the Wellesley's military map and sits next to the Prince Regent (Blackadder). This angers Wellesley who beats Blackadder (Prince Regent) and tells him off, recounting how he was told the Prince Regent was the moron and his servant, Blackadder, was a respected figure (which was true). After finally kicking Blackadder (Prince Regent) out for delivering coffee instead of tea, Wellesley departs but reiterates the duel is still going to happen.
On the day of the duel, the Prince Regent (Blackadder) is surprised to hear they won't be using traditional swords or pistols, instead Wellesley has decided the duel shall be fought with Vickers-Armstrong 4-pounder cannonettes.
The Prince Regent (Blackadder) survives the duel as Wellesley's cannonball was blocked by the Prince Regent's (Blackadder's) cigarillo case which Wellesley previously gave to him. Wellesley, having grown fond of the Prince Regent (Blackadder), sees his survival as God sparing him for greatness and declares the duel a draw.
Blackadder (Prince Regent) then arrives and attempts to end the scheme by announcing himself as the real Prince Regent. Wellesley, not believing him, is outraged that Blackadder (Prince Regent) would be so disrespectful to the Prince Regent (Blackadder) just moments after he survived an honorable duel, so he pulls out a pistol and kills him.
King George III, who has become completely mad to the point he is unaware his son was killed and replaced by his butler, then arrives after hearing news of his son's presence there and announces his wish for the Prince Regent (Blackadder) to marry a rose bush. The Prince Regent (Blackadder) decides to continue being the Prince Regent and King George is for the first time proud of his son. The Prince Regent (Blackadder) invites Wellesley to dinner at Buckingham Palace as they have "a lot to thank [him] for."
Wellesley agrees and tells him, though his father is mad, that the Prince Regent (Blackadder) has "the makings of a fine King."
In Blackadder: Back and Fourth, Lord Edmund Blackadder V uses the time machine and arrives during the Battle of Waterloo and accidentally kills Wellesley by landing the time machine on top of him. Due to Wellesley's death, Napoleon wins the battle and when Blackadder arrives back to New Year's Eve 1999, the French have taken control of the United Kingdom. When Blackadder reverts all the previous changes he made to history, he doesn't land the time machine on top of Wellesley and instead wishes him good luck at Waterloo, this restores the timeline to where Wellesley defeated Napoleon at Waterloo.