mysterious grass

These are some photos of a mysterious grass that my friends saw on October 1st just above Lulworth Cove, on the Purbeck Hills in Dorset.

It's hazardous to attempt to identify something from a photo when you've never seen it before, but I feel reasonably confident that it is a proliferous form of Cocksfoot (Dactylis glomerata), on the basis e.g. of the leaves, ligule, and the putative inflorescence, both branched and congested. I know Cocksfoot does proliferate sometimes, in SW England among other places. The only image that I could find on the internet looked very different, but then it was taken at a much earlier stage of development.

My main doubt is whether it might be, not a proliferous form, but a mutation caused e.g. by a gall. In other words, are we looking at little plantlets within the spikelets, or have the spikelets themselves been replaced by leafy growth? I'm not sure, but in the closeup below I think you can make out the glumes. Anyway, if it was a gall you wouldn't expect it to affect the whole plant.

As ever, I invite anyone who knows more about it to confirm or correct....

I've found it myself now:

Proliferous Cocksfoot (Dactylis glomerata). Southwick Country Park, 4 August 2020.