My template's <head> tag is defined as a snippet combined with preload replace variables, as per Low's idea (http://gotolow.com/blog/snippets-and-preload-replace-variables). On one or two templates, however, this technique won't cut it and I need to use a full embed. That's a shame, but there you go.
Thing is, I'm finding that if I am logged into the CP as an Admin (a member group I created for the client to use for basic site editing, with much less control than a superadmin), the embed doesn't embed. So the page has no <head> tag at all, with all of the rather unfortunate consequences that that implies.
I'm racking my brains to think what setting in the member groups settings might be causing this; if I'm logged in as a super admin (or not logged in at all) then the embed is processed normally.