Vogler was a German arms dealer in 1937 who sold guns to Hsien-Ko.
Inspector Sung-Chi Li found out about an arms deal that Vogler was going to make with Ko at the docks. The deal was interrupted by the Fourth Doctor and Romana I, which made Li and his men move in to arrest them prematurely. Kwok shot and killed Vogler to prevent him from identifying him and Ko. (PROSE: The Shadow of Weng-Chiang)