the lead role
This film has a lot of intelligence, some good acting and very good moments. It has the feel of something edited a shade abruptly to get down to around a more commercial 2 hours. Maybe commercial considerations decreed that the actor in the lead role had to be American, I don't know. But the character is English, and even after looping Robert Morse doesn't sound convincingly English, and in my view (and that of others, it seems) his is the least satisfactory performance in the film, accent aside. I can't help thinking it might have been an idea to choose an English actor. I can imagine for example Tom Courtenay, or possibly David Hemmings, giving the film a boost. (A few years later, Michael Palin would have ticked the biscuit.)
Postscript: But of course! it just needed Sir Francis Hinsley to "straighten him out on the accent bit"...
"I beseech ye in the bowels of Christ, think that ye may be mistaken."