Hemming, A. O.
Alfred Octavius Hemming (1843-1907) trained as an architect in Edinburgh before joining the firm of Clayton & Bell in 1868. He set up his own studio in London in 1883. The firm continued after his death under Rupert H Corbould.
Source: Stained Glass Marks & Monograms, complied by Joyce Little, and edited by Angela Goedicke & Margaret Washbourn (NADFAS, 2002)