The Junior Constitutional Club was a gentlemen's club at 101 Piccadilly. It was formed in 1887 following over-subscription of the Constitutional Club, and like its older sibling it was politically aligned with the Conservative party. It was, briefly, one of the largest clubs in London, with 10,000 members by 1890.
This reference would have quickly dated Dracula for London readers, however, because despite its initial popularity the club had closed by 1904, just seven years after the book's publication. The building is now the Japanese Embassy.