Question: Which historian commented that the king's act in associating with Chamberlain as unconstitutional?
Sentence: While broadly popular among the general public, Chamberlain's policy towards Hitler was the subject of some opposition in the House of Commons, which led historian John Grigg to describe the King's behaviour in associating himself so prominently with a politician as "the most unconstitutional act by a British sovereign in the present century".
Answer in sentence: yes