Costuming spread with the science fiction conventions and the interaction of fandom . The earliest known instance of costuming at a convention in the United Kingdom was at the London Science Fiction Convention ( 1953 ) but this was only as part of a play . However , members of the Liverpool Science Fantasy Society attended the 1st Cytricon ( 1955 ) , in Kettering , wearing costumes and continued to do so in subsequent years . The 15th Worldcon ( 1957 ) brought the first official convention masquerade to the UK . The 1960 Eastercon in London may have been the first British-based convention to hold an official fancy dress party as part of its programme . The joint winners were Ethel Lindsay and Ina Shorrock as two of the titular witches from the novel '' The Witches of Karres '' by James H. Schmitz
15th Worldcon
15th World Science Fiction Convention
Cosplay