Is this perhaps the point? Windowsill gives short fat shoots, in dark
long impractical vulneralbe ones?

Well, for a bit of a laugh, I've potted up those potatoes of mine which had
'long impractical vulnerable ones' into 2 ltr plastic drink bottles, after
having chopped off the tops of the bottles. Put the tubers in right at the
bottom, and have 'earthed' them up as they have grown. They are now all
above the height of the bottles with very healthy looking leaves. The
compost is now at the top of the bottles.

I'll plant them out when I get down the lotty by simply sliding the plant
into a suitably shaped/sized hole.

Got the idea from the instructions that came with my potato barrel, which
uses a similar technique, i.e. gradual covering of the tuber shoots as they
grow up from the bottom of the barrel.

Best,

- h