Can you help us track down a mystery Rubus?

Martin Godfrey has been in touch about his current project at Stoke herbarium. He is "cataloguing a few boxes of Eric Edees's Rubi which don't seem to have been looked at before.  Nice stuff and a number of isotypes, however I have a folder of material which appears to be of an unpublished species - Edees calls it R. subdurescens as it is somewhat similar to R. durescens". 

Edees is responsible for the Flora of Staffordshire (1972). 

Martin goes on "There is an interesting letter in with the sheets from a Roy Smith talking about the features which distinguish the new material. I would be grateful for any information which may be known about this "species" (nothing obvious on an internet search) - if none, then it might be a nice opportunity for a publication for someone keen on the genus.  

"Once I have finished the catalogue, I will get it put on the BSBI web site as I suspect that Batologists will be unaware of this material".

So, can anyone help Martin find out more about this taxon? Leave a comment below if you can help or email me at louise.marsh@bsbi.org and I'll put you in touch with Martin. 

He has kindly sent along an image of "what would have to be the "type" specimen [above] plus one [right] of its label".