This is a poor version of the Marconigraph pic, Jo. It is the standard image of Durrant and has been widely used.
Ing, I would like to see whatever you have of JD. If it is not too much of a secret, it might be easiest to stick it up here.
I looked through some of the CR10s in the last fortnight with Joanne Smith of SCC.
I have never seen a W/o there and she or her colleagues has never found one for me in a couple of searches. I suspect Marconi employees were not "merchant seamen." But you may be more familiar with them.
The good news is that a picture of Fred Barrett has turned up - a vital witness at the British and American Inquiries who has hitherto been faceless. Definitely the right man. One or two other goodies also.
Some of them could go up here on ET in due course.