The New Popular Edition 1:50,000 maps were based on surveys conducted between 1914 and 1948 and published between 1945 and 1948. Available here in greyscale, they were a hybrid of the “Seventh Series” maps that would follow them in the 1950s and the Popular Edition maps from the 1920s.
A search found several places but couldn’t find Hackney! Navigating the collection is awkward; moving to an adjacent area map is impossible.
I prefer the NLS map facility.