In Aquamacs, the Emacs for macs, the dictionary can be changed in the Menu by going to Edit -> Spelling -> Change Dictionary...
In my case, I enter en_GB. How do I avoid doing this for every file again every time I open it? Where can I set this permanently as the default for all files?
I suppose I need to add a line in Preferences.el - but which one?
Neither of these two lines work
(setq ispell-dictionary "en_GB")
(setq ispell-dictionary "british")