On This Day – 21st May
1420 The Treaty of Troyes was signed, in which it was agreed that Henry V would marry Catherine, the daughter of King Charles VI of France and that Henry and his heirs would inherit the throne of France upon the death of the French king. The treaty was undermined by the deaths of both Henry V and Charles VI within two months of each other in 1422. https://en.wikipedia.org/wiki/Treaty_of_Troyes

1471 Henry VI, King of England, was murdered in the Tower of London where he had been imprisoned by Edward IV, who then resumed the throne. https://en.wikipedia.org/wiki/Henry_VI_of_England