Identify Potato Problem

This is a pic of a problem I am finding with the last of my potato crop.They are the last of my Cara maincrop and one in ten I am finding with this inside.There is no obvious signs of entry but I would be grateful if someone could identify it for me please.I also grew Maris Piper,Estima,Kestral and Pentland Javelin but it was not in any of these.
Thanks
Mike

just read this in my book : blight - 'blighteed tubers develop dark patches on the skin, with firm reddish-brown rots below.'  looks like you've got blight to me!

Spraing?

Click on top image.

looks like what i have in some of my picasso to

Spraing?

Click on top image.

Thanks Dave.That looks like it.Are there any solutions?

Mike

Thanks Dave.That looks like it.Are there any solutions?

Mike

I'm not saying it is it, a I've never come across it. It's only what I've read about - even before this forum existed.

There are many causes, already infected seed spuds, nematodes, dry spells etc.... Dr. H says to practice crop rotation and avoid Pentland Dell which is particularly susceptible.