Mysterious jellyfish

This is reported to be the first of it's kind. Quite how, I'm not sure. Discovered this in my little brother's pupil/parent school paper. It measures a massive 250m long by 60m wide.  The pattern was created  in a field near Ashbury in Oxfordshire. The owners are demanding the public stay off their land due to the damage. It's probably a better view from the air anyway. The big secret as to how these designs are done make them of endless intrigue to me.