I dug the plants up carefully so I could tell which spuds were the old
seedpotatoes and which were the babies. Usually by the time you harvest potatoes, the seed tubers have gone soft and slimy, but at this early stage they're still firm and look just like any other spud. They're not good to eat though. All their reserves have gone into making a new plant and they're crunchy (why?) and tasteless, if you accidentally cook one and eat it.
Somehow at this time of year it seems worthwhile preparing potatoes that are barely bigger than peas.
This makes a much better lunch than rose bay willow herb!