There's a bit more biographical information in the introduction to this book, edited by Tom Fort, which is almost "H T Sheringham's Greatest Hits"
http://www.anglebooks.com/product.ph...d-by-tom-fort-
It's a very good read indeed. Some of the stuff about Blagdon is astonishing to the extent that, in effect, he says "...carry a lure rod and a nymph rod..." so he'd forecast the essence of modern reservoir trouting - before 1914.
Quite sad that Sheringham had a nervous breakdown through (over)working for the Government during WW1, and seems never to have been quite the same after that and until his early death in about 1930.