This is called PHACELIA (or 'fiddleneck')

During today's country walk with friends Monique and William, the public footpath took us through a field of these plants: W, the expert told me the name Google says: "Phacelia used as a soil improving green manure It is effective at preventing nitrogen leaching and suppressing weeds, due to its fast establishment. Although not known as a deep rooted species, its dense zone of shallow roots are very good at conditioning the top 3-4cm of soil." I couldn't resist including the butterfly photo as an extra (taken during the same walk) It's a Small Tortoiseshell, a better example cf the one I posted on 9th June