J. Roy Lancaster
We have discovered two facts about a John Roy Lancaster:
In 1911 he was working for Messrs. Horne & Co, Auctioneers and Surveyors of 85 Gresham Street, and of 35 Old Queen Street, involved in the sale by auction of the Crystal Palace in Sydenham.
He was a director (along with William Edgar Horne) of the Prudential Assurance Company from about 1920 to about 1940.
We are guessing that the J. Roy Lancaster on the plaque is the same man and that he or one of his companies owned or managed 7 Edgware Road.