The first is incorrect in BrE.
Are you sure?The first is incorrect in BrE.
That comes second in your post.Are you sure?
The Cambridge dictionary says we must write separately.
never mind
1. used to tell someone not to worry about something because it is not…dictionary.cambridge.org
That's right.Are you sure?
The Cambridge dictionary says it's a two-word phrase.
never mind
1. used to tell someone not to worry about something because it is not…dictionary.cambridge.org