Masterclass or Master Class?

[bradsmissus]

Hello lovely pedants!

Is it all one word?

If not, is the class with a capital c?

[Paranoid about spelling/grammar in pedant post]

I've only ever seen it written as "masterclass" or "Masterclass", never as two separate words.

It appears, from many Google results I did regarding this same question, that either form is acceptable, and it is written either way. Most notable example of the two-word version is the play "Master Class" about Maria Callas. Personally, I prefer two words. If written, master class is not normally capitalized as it is not a proper noun ("I went to master class today."). If using it in advertising, for example, for a master class with a specific person, I would capitalize both words as it would then be a formal title ("Please register to attend the Marilyn Horne Master Class.").

I think the meaning would be different. Masterclass- a specialized class run by an expert etc. Master Class- a class for a master's course, or a cunning play on words like the Callas play.

To define by locality then, in the US "master class" is two words: www.merriam-webster.com/dictionary/master%20class
In the UK "masterclass" is one word:
en.oxforddictionaries.com/definition/masterclass
So, personal preference is the watchword - or is that watch word?