Make sure you scroll through the whole font list. Some fonts that ID cannot otherwise identify wind up at the bottom, and some fonts are listed out of the expected alpahbetical order.
YuO can also try deleting the Adobefnt*.lst files where * is a two-digit number.
Thank-you for your reply... I've checked the entire font menu and cannot find a trace of it.
I've never tried to delete a .lst file before. Where can I find this?
Use the search function in Finder. Used to be called Spotlight, I think?
Sometimes font works differently. In most cases they duplicate or they have different filenames. And sometimes lower version of InDesign interpret fonts entirely different in names.
If you don't have font handling app, sometimes InDesign don't update it's font list automatically. You have to Quit and Re-Open InDesign, and sometimes they conflict with .OTF or .TTF if they both been installed.
You can try these if it works with you. Just copy the font directly in Application -> Adobe InDesign -> Fonts folder.
But the downside of this one is you could only use that font in InDesign. If you want to use it for all your application then try if your Font is detected by InDesign or All other application in different filename.
Maybe they are name as BelfastSF of Belfast-SF.