Problem displaying related foreignkey data in Django Admin screen

Question

To display foreignkey data in my admin list view, I created a callable:

def next_date(self):
    EvDateObj = EventDate.objects.filter(event__id__exact=self.id)
        .exclude(event_date__lt=datetime.date.today())
        .order_by('event_date')[:1]
    return EvDateObj

This shows in the list view as:

[<EventDate: 25 September 2010>]

Which is the unicode string for the EventDate model (25 Sept 2010), with some django-generated object stuff around it: [< EventDate ______ >]

If I modify the callable return statement to try and just get the date itself:

return EvDateObj.event_date 

or

return EvDateObj.event_date.strftime("%d %B %Y")

the admin list view simply shows:

(None)

Any thoughts? I am unsure how to proceed because I can get the desired object, but cannot access any of its properties without triggering the "(None)" result.