WI England wins the hundred years war
In 1420 it looked like the England had won the hundred years war: Burgund had agreed to an alliance, much of northern France (including Paris) was concered, but most importantly queen Isabeau had declared her son to be illegitimate (thus excluding him from the succesion) and Henry V. was choosen to be the next King of France and married the daughter of the former french king.
But then the Scots intervened and managed to defeat the English at the battle of Baugé. The defeat itself wasn't that important, but it forced Henry V. to return to the battlefields, were he died of an illness.
So what if the english manage to win the battle of Baugé, thus preventing the early death of Henry?