Some of the plants are protected by a plastic "Seedling Greenhouse" affair, with a zip-up lid:
This thing was intended primarily to protect plants from frost, which it has done well, but it has also served to protect then from the rain, which has been more of a threat this year than frost. The potato plants inside are a lot further advanced than the ones outside, although they were only planted a week earlier.
Next door to the Seedling Greenhouse are my second batch of potatoes, growing in containers that originally held pelleted chicken manure. Here you can see them (left) covered with a wire grille to prevent foxes furtling around in the compost.
The last batch of potatoes, round the side of my house, is the most under threat. They get all the rain, but because they get little direct light or breeze they don't dry out so well when the opportunity arises. I have been wondering if they would suffer because of this, but they seem to be doing OK. Their compost is completely sodden, despite the presence of many drainage holes in the pots: