I may be being paranoid, but I'm wondering about shelving our plans to make mustard paste from the wild turnip seeds we collected.
Wild varieties of Brassica rapa - like the one we've been picking - can have a lot of erucic acid in the seeds. (Apparently nasturtium seeds are also rich in it).
On the other hand, we only collected a miniscule pile of seeds, and from what I'm reading in articles from various food safety authorities, a tiny bit consumed on a very occasional or short-term basis is probably okay.
I'll do a bit more research.
As a plan B, there's some Shepherd's Purse, another member of the mustard family, growing along the bank beside our house. Perhaps we could try making mustard from the seeds of that instead (assuming they are less rich in erucic acid).
They're absolutely tiny, those Shepherd's Purse seeds, and it would be fiddly, but it could be fun. My daughter is already quite taken with this plant's little heart-shaped seed pods.