However I don't think that he would have opposed the parliament in it's actions in the early years of the war and pushed for capitulation without invasion or starvation.
He doesn't need to do anything at all in Public. Just one small action imagine if he privately spoke to Lord Halifax about the PM post and made it clear that the country needs him etc. The King doesn't have to be publicly anything. A conversation with the King would be a major pause for thought for any politician.