I kind of figured his accent was put-on but he is from England. He was born in 1910 in Belgrave Mansions, London. But perhaps his accent is "put-on", just like most other actors of his time. They were taught a screen accent, whether it was American or otherwise.

This would explain Shirley Jone's abominable use of the word "fer" in all of her unfortunate Rogers & Hammerstein musicals. She spoke perfectly articulated English except for a few words thrown in to make her sound like she was from the country. "What ya gonna do that fer, Curly?" Let's just say it DIDN'T work. Just makes my skin crawl to hear that!