[Math] Raoul Bott’s quote on Morse Theory cited by Bestvina and Kahle: where is it from

Question

I wanted to properly cite the following awesome quote:

Every mathematician has a secret weapon. Mine is Morse theory. – Raoul Bott

Now this has been attributed to Bott in precisely two places that I can find: the older of the two is Bestvina's work on PL Morse theory here and the more recent occurrence is in the 14th slide of Kahle's talk available as a rather large pdf file here.

Question:

What is the original reference for this quote?

I've combed through the likely suspect, Morse theory indomitable available here but the quote does not appear to be in that paper

Answer 1

Here is Mladen's response to my email asking this question:

I heard him say it in a colloquium talk in 2001 (I think).

Case closed, unless Bob MacPherson has a different answer.