Carol responds:

I agree. Interesting, isn't it, that almost all historians suspect the truth of the official version of Henry VI's death, noting how convenient it was for Edward IV (and, too often, making Richard Henry's killer, but that's a different matter), and yet they accept the story that Humphrey died (equally conveniently and after three days in prison) of a stroke. Could we be seeing a pro-Lancastrian bias among historians here?

Marion responds:
 
I think it's more complicated than that.  I don't remember the details, but some later historians disagreed with the "Good Duke Humphrey myth."  I think it had less to do with a pro-Lancastrian bias than a bias in favor of one or more of Duke Humphrey's many political adversaries.  Or, in some cases, maybe the label "Good Duke Humphrey" provoked efforts to prove he wasn't really as good as people thought he was. 
 
The more I read about Duke Humphrey, the more I felt his reputation had in common with Richard III's.  Not because he was ever accused of murdering anyone, but because some historians seem to have given his flaws and mistakes higher priority than his contributions to English scholarship and his strengths as a law-enforcer.  I use the term "law-enforcer" because his conflicts with Henry Beaufort, bishop of Winchester (who was called "the rich Cardinal" by his contemporaries;  the sources of his wealth were questioned then, and haven't yet been identified)  make the term "peace-keeper" sound ironic.  I don't mean to be ironic about Duke Humphrey.  I respect his contributions, and I think political fights have unfairly hurt his reputation.  He was a political loner, maybe too idealistic, and scholarly opinions seem to favor those who defeated him.
 
Marion