Pea Blue?

There's this field I pass on the way to work which is just outside St. Albans. I've noticed, briefly as I zip past, that it is now awash with blue. So today I thought I would stop and take a closer look.

It's actually only really blue at one angle - the angle I see it from my bike. The plants are far apart and similar to rape seed. The delicate poppy-like leaves remind me of sweet pea. Does sweet pea come in blue? Would you get a whole field of blue?

I reckon its some sort of fallow, nitrogen fixing crop, but gosh, Im no farmer or gardener so what do I know.

It looks beautiful to me. I know that.

Update: Good job I took the photo when I did because the next day all the flowers had gone. The crops were still there, just no blue anymore. Curious.