Rachel Aitch wrote:
Quick question: one of my clients (I'm a professional gardener, but
don't hold that against me) asked me why his entire potato crop, of
various types, turned to mush as soon as they were put into boiling
water.
I have no idea!!
Desperate to preserve my reputation, I turn to you (picture me with
hands out, pleading) for suggestion...

I've asked around because I never heard of this before. We all came to
the same conclusion - your client had cut his potatoes in very small
chunks and they cooked faster. I do this when I want a very nutritious
soup in 20 minutes. Also it depends on variety. Do you know which one
he grows? Having said that, I've found that baked potatoes are superbe
for roasting in small chunks like chips, with skin on. My experts here
are unamimous, they are 16 and 11 years old )