The Man With the Twisted Lip - Facts

 

The story starts with Watson going to an opium den. An opium den was an establishment in which opium was sold and smoked. Opium dens were prevalent in many parts of the world in the 19th century, most notably China, Southeast Asia, North America, and France. Victorian London's reputation as a centre of opium smoking is based on literary fiction rather than historical fact. 

Neville St Clair was from Lee in Kent. Lee is an area of South East London. It was in Kent before becoming part of the County of London in 1889, and then Greater London in 1965.

The man who Mrs St Clair comes across is a Lascar. A lascar was a sailor or militiaman from the Indian subcontinent, Southeast Asia, the Arab world, British Somaliland or other lands east of the Cape of Good Hope, who was employed on European ships from the 16th century until the mid-20th century.