When researching it is always a good idea to try different variations of how things could be written down. In this case, trying N.S.II instead of N.S.11 we unearthed a photograph of N.S.11 flying east over Southampton Row, London. The hoardings on the right cover the future site of Victoria House which was built in the 1920s.
The photograph is from Sapper Francis McFarlane’s photographic album (P1193-024-088f) in the University of Otago, Hocken Collections – Uare Taoka o Hākena, Aotearoa (New Zealand).