Hah I should have looked at the help before!

My first instinct was to try :e without any arguments.

I looked at the help for this and a bit further down is

:ene[w] Edit a new, unnamed buffer. This fails when changes have been made to the current buffer, unless 'hidden' is set or 'autowriteall' is set and the file can be written. If 'fileformats' is not empty, the first format given will be used for the new buffer. If 'fileformats' is empty, the 'fileformat' of the current buffer is used. {not in Vi} 

The answer is to use :ene[w]

Hah I should have looked at the help before!

My first instinct was to try :e without any arguments.

I looked at the help for this and a bit further down is

:ene[w] Edit a new, unnamed buffer. This fails when changes have been made to the current buffer, unless 'hidden' is set or 'autowriteall' is set and the file can be written. If 'fileformats' is not empty, the first format given will be used for the new buffer. If 'fileformats' is empty, the 'fileformat' of the current buffer is used. {not in Vi}