Looking at them the other day, I noticed that the leaves on two of the plants were yellowing and had black spots. I don't think my photo gives a true likeness of it, but the nearest I could come to it in the book was mosaic virus.
There was only one thing to do - dig them up as fast as possible and don't let the debris anywhere near the compost. That deed duly done, I was surprised to find that the two plants wielded nine extremely healthy looking potatoes.
They are in the kitchen, ready to accompany a suitable meal. Result (subject to taste)!
