Bingowings, you seem to be the guy to ask (Given your Whovian knowledge and current Avatar):
I started watching 'The Sea Devils' this afternoon for the first time (Not seen a great deal of Pertwee serials to be honest) and I was very surprised (Perhaps even shocked) by the friendly way The Master greats The Doctor and Joe and they seem to like him in return. I thought they were mortal enemies? (I know they weren't back in the early days on Gallifrey).
I'm more familiar with the later 80s Master who was often cheeky and full of mischief but never friendly with The Doctor. Can you elaborate on what serials came before 'The Sea Devils' and what changed afterwards to the character?
btw I noticed 'Irish Jabba' aka Declan Mulholland is in it...
It was his very distinctive staccato Northern-Irish voice I spotted rather than the face, but it is him.