Delete confirmation page in Django admin not displaying child records

[Derek]

Using Django 1.6.11

I have just noticed for a few cases (at least) that, while delete confirmation page in Django admin shows as usual in my app, it does not also show the related child records that will be deleted when a parent record is selected (the confirmation page only shows the parent record).  I ran a separate test using this code - http://thirld.com/blog/2012/09/17/django-enumerate-related-objects-cascade-deleted/ - which shows that there, in fact, related records.

(I do not - yet - have tests that would have showed me when this functionality stopped working; I had assumed that, because it was part of Django, I would not need tests for this.)

Any ideas why this happening and how to "revert" to the expected behaviour?

Thanks

Derek