This is Martin Boon - one of the most prominent of Clerkenwell ultra-radicals from the late-1860s to the mid-1880s. I have spent quite a lot of time and effort tracking down the details of his life - but it's only very recently (February 2014) that I have seen his likeness for the first time. The entries on Boon on my blog tell the story, and it's quite a story, and they prompted Boon's great-great granddaughter, Laura Boon, to get in touch, and she has provided this marvellous photo (and given her permission for me to post it here).
So who is Martin Boon, and why does he matter? Well, rather a long time ago, I wrote an entry on him for the Dictionary of Labour Biography, and I have posted that below. He was a difficult and quixotic character, but also one of the most determined advocates of land and currency reform - very much the agenda he imbibed from one of the most noteworthy of Victorian radicals, the one-time Chartist, Bronterre O'Brien.
The citation details of the article are:
Andrew Whitehead, 'Martin James Boon' in Joyce M. Bellamy amd John Saville (editors), Dictionary of Labour Biography vol. IX, Macmillan, 1993, pp.9-16