The Mountbattens were definitely not Commoners. Lord Louis Mountbatten's sister was the mother of Prince Philip, the Queen's husband. Lord Mountbatten was a naval officer; from 1943-46 he was Allied Supreme Commander, South East Asia Command. It was/is not universally agreed that he was deserving of a high post.
BTW, it's Chamberlain.
I was typing while driving and I got auto-corrected, which is really nothing new. My wife does it all the time.
I couldn't think of anything witty to say so I left this blank.