The entire site has been hit by potato blight. Lost about 1/3 of the Desiree crop, cut off the exposed foliage last weekend, then unearthed the potatoes last night. A lot of them had been infected, including this monster:

Still, managed to fill a large bucket of good potatoes so could have been worse.
The tomatoes, on the other hand, have been a total loss. Another week and I might have been able to pick the first ones, but the blight got there first and the whole lot had to go on the bonfire.