Start your talk exactly this way:

(Thank the other speakers... Then in your segue into your talk... "We just finished singing 'Come, Come, Ye Saints'' - a wonderful hymn that has an incredible story behind it. The author of the hymn... "

Then PAUSE, suck in your breath, and after an uncomfortable pause say "... No, I'm not going to talk about that... For some reason I feel prompted to now speak about something a little unorthodox but perhaps it's exactly what one of you needs to hear right now..."

After that intro you can literally talk about anything you want.

(Note that I didn't explicitly state WHAT the prompting was coming from, you could just be prompted by your own desire to talk about football...)