That's what I call an all star cast though the film does skate over the less seemly aspects of More's life. Leo Mckern is great as Thomas Cromwell.
"I show you the times."
IIRC the movies covers about 5 years, from the time More became Chancellor of England until his death, beheaded for treason.
Robert Bolt intended to show More's character in standing by his convictions whatever the cost.
All he had to do to avoid that pesky beheading was to publicly admit that Henry was Supreme Head of the Church in England; i.e., admit to the legitimacy of the Act of Supremacy.
Consider what he risked by not doing so: The rack (in the beginning), but Henry's conscience wouldn't permit it.
Later, whilst imprisoned in the Tower, he tells his family that he is "sick with fear over what they might do to me."
What they "might do to [him]" is what they did to all traitors: draw and quarter them, this after first parading them through the streets naked.
More did not know at the time that Henry was going to spare him that ignominy and subsequent torture, and allow him a quick death at the block.
So despite his certainty that he would experience D&Q (he was a lawyer, he knew the punishment for treason) he still stood fast in his convictions.
I put this to question to anyone: How many of us would be able to do that?
All you'd have to say to avoid all that excruciating horror would be to say, "Yep Harry, old son, you head the Church here in England, whatever that old guy in Rome may say."
But he didn't .
Not the only man of those times (Catholic or Protestant) to display the courage of his convictions to the point of death, but an admirable example, none-the-less.