Mikey wrote:
I always find the accidental ones give the biggest crops... compared to
the ones I care for lovingly, loads of compost in the trench, earthing
up, watering etc. etc.

I've noticed this: I supsect that, being waiting in the soil, they can
get a head start if the conditions are favourable in advance of you
having time to plant seed potatos. It's not a relaible phenomenon