was burnt alive, but I forget what for.

It was heresy, and I don't think a parson's daughter would actually forget something like that. Cobham was part of an early Reformation movement (a hundred years prior to the Protestant reformation of the 1500s.) It was known as Lollardy.

Cobham, aka Oldcastle, adopted Lollard opinions after the churches on his wife's estates were laid under interdict for unlicensed preaching.

Cobham was accused of heresy. But his friendship with Henry prevented any decisive action till convincing evidence was found in a book belonging to Oldcastle.

The matter was brought before the king, who desired that nothing should be done till he had tried his personal influence. Cobham declared his readiness to submit to the king "all his fortune in this world," but was firm in his religious beliefs, which eventually led to hed condemnation and he was hanged (as a traitor) and burnt (for heresy) -- but if he really was alive at the time is uncertain. Other accounts have that he was drawn, too.