Just spent a while keying this one out. There's a small stand of it down in the orchard towering majestically above the Ox-eye daisies and other grasses.
Yesterday I failed to ID it, but today, using the key from the grass ID workshop I went on the other week (courtesy of the National Plant Monitoring Scheme, BSBI and Reading University) and my stereomicroscope, I got it.
I must say how much easier it is using the x20 setting on the microscope compared with a x10 hand lens. The colours and details of the glumes; the fact that the lower floret was male and the upper bisexual; the scabrous nature of the rachis and the twist in the lower lemma's awn were as plain as day.
There really is a whole world of beauty beyond our visual limits and I can't recommend a stereomicroscope enough. You can pick up some really good ones on eBay for under £100.