(2-part post):
Hi Dot
I saw that screen name somewhere else on AB and I wasn't sure if it was the 'real' you. Your post about a shoe shop confirms your identity ;-)
The defect with the shoes is definitely not due to an inherent fault. If the guy tries to insist upon a refund (while no doubt shouting about his 'rights'), my response would be to say something like this:
"Well, if you insist, I'll send the shoes off to our forensic staff so they can determine why the heel snapped. If they find that it was due to poorly manufactured heel, I'm sure that my boss will be happy to authorise a refund. Of course, if their report shows that the damage was deliberate, they'll probably seek a prosecution, under Section 16 of the Theft Act, for attempting to obtain a pecuniary advantage by deception. It's your choice".