In Private Eye magazine, Liz Mk2 is allus called Brenda 
The rest of the royal entourage are also given names other than their own, I forget them
A quick Google:
The Prince of Wales (Charlie)=Brian
Philip= Keith
The late Margaret= Yvonne
The late Diana= Cheryl
I do believe that on one occasion Philip was called Stavros
For some reason, I find this unbelievably amusing.
Well he was born on Corfu, one of the Greek islands.
Imagine if he’d been born on Lesbos
Brenda would have been married to a lesbian 
Actually, I heard that she and the entire royal family are secretly giant intelligent lizards…
“Secretly”?
“Intelligent”?
Hey, it’s not my delusion. Google “David Icke” sometime…
Thank you for the correction, APB, I hadn’t realized that. Regicides was clearly an accurate term then!
Cromwell himself was offered the crown at one point but declined to reign as monarch. He was created Lord Protector, a title and position which passed to his son Richard after his death. (The latter was known as Tumbledown Dick owing to the brevity of his tenure).