The office of the Queen's Champion is an important hereditary office in the United Kingdom that apparently dates back to 1066. The duties to be performed in exchange for the 12 km² Manor of Scrivelsby are not manifold, but all the more dangerous. Until the coronation of George VI in 1821 his duty was to challenge to duel those who would not accept the new monarch.
At the coronation banquet he would throw down his gauntlet three times and a herald would issue a challenge among the following lines:
If any person, of whatever degree soever, high or low, shall deny or gainsay our Sovereign Lord George, King of the United Kingdom of Great Britain and Ireland, Defender of the Faith, son and next heir unto our Sovereign Lord the last King deceased, to be the right heir to the imperial Crown of this realm of Great Britain and Ireland, or that he ought not to enjoy the same; here is his Champion, who saith that he lieth, and is a false traitor, being ready in person to combat with him, and in this quarrel will adventure his life against him on what day soever he shall be appointed.
The champion was loaned the second best horse in the Royal Mews and an armor which was his for the keeping if anyone took up the challenge and the champion has won; otherwise he would get a cup from which the sovereign has drunk the champion's health.
There are no certain records that would show that anyone accepted the challenge, though there are some rumours about different Jacobites doing so.
After George VI the tradition of holding a coronation banquet in Wetminster Hall (the building of the Houses of Parliament) was abandoned and thus the life of champion became simpler, until the 20th century. In 1902 the then champion petitioned the Court of Claims -- the special court set up at every coronation to decide on who gets to perform what service at the coronation -- and since then his duty is to carry the Royal Standard at the coronation.
Find out more on Wikipedia; the painting comes from this website. A nice way to learn about chivalric traditions and the way a proper challenge was accepted and fought out is to read the Song of Roland from the eleventh century.