Descurainia sophia Flixweed C DD N?
I have occasionally seen this possible native around waste sites and verges in various parts of the country but in this set-aside field in Breckland it was abundant. Although it is a yellow crucifer which are notoriously difficult to identify, this plant has very characteristic feathery leaves and small flowers. Originally known as Fluxweed, it was thought at one time to be a cure for dysentery.
D. sophia is most frequently recorded from east Anglia in England but is dotted around the country with concentrations around Inverness for example. There is not much to be found in Ireland.