This quite lovely wildflower, the Corncockle, has grown from a Wildflower seed bomb mix I sowed in the Spring. 
My wildflower guide says  "With modern farming practices, this plant has gone from being a familiar cornfield weed to a rare wildflower, both in  farmland and in the wild.  However, it is still much used in wildflower seed mixes".   That's good news as its such a pretty flower.
The guide also says "The Corncockle's poisonous seeds may contaminate flour, which is why farmers have, over the years, worked to eradicate the plant"
I'll still try to harvest some seed, but only to grow - not to eat !!