This flower I am not a hundred percent certain about the identification but I think it is Nipplewort (Lapsana communis). It certainly is a common yellow flowered plant and is not confined to this particular habitat in the strip of arable weeds that I have been investigating. There are so many similar yellow flowered plants that I am never absolutely certain what they are. Anyway, this is my best attempt. If you know better, please do let me know.

Nipplewort is said to have useful medicinal and culinary properties.

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