Admin user can't manage fields on custom content type When in logged in to my Drupal 7 install as the administrative user, I can't access the "Manage fields" or "Manage Display" for my custom content types.

I've tried all the following with no joy:


I've deactivated all my custom modules
I've given the admin user all permissions
I've flushed the cache, many, many times
Logged out and back in


I'm pretty sure I'm not using the hook_drupal_break hook anywhere!

I've got NO IDEA what I've done wrong. It used to work, but now I can't access it.
I feel so stupid. But I'm leaving this answer so that the next person to have this same problem will save 3 days of development time:

The module that allows fields to be created on entities (nodes, user etc.) is creatively called "Field".

But, that doesn't mean you'll have a UI to create/edit them. There is another creatively named module called "Field UI". If this modules isn't installed AND enabled you won't have a user interface to edit your fields...