Could be Phacelia tanacetifolia, often grown as a green manure, hence a field of them, only a guess.

That would be my guess to Jimmy, google Phacelia tanacetifolia images Strawson.

Welcome to GoY and yes I think it is that too. I had some as a bedding plant a few years ago.

Yes that's it - we had a self sown one once that puzzled us for ages - surprisingly even the man at our local nursery didn't know what it was! I love the shape of the flower and the way it unrolls itself.

Thankyou for your helpful answers .i think it fits the bill having been grown on such a vast scale and on an apple research centre.

These are sometimes sown for set-aside, that is the headlands of the fields that Farmers leave for wildlife (they get paid to do that). Possibly they were sown to encourage the bees into the apple blossom area, though whether they flower at the same time - not sure!