The title "Lonely Londoners" is directly related to the novel's main theme. The main character, Moses Aloetta, is an emigrant from his native Trinidad to England, and specifically London, in the years after World War II. The central theme of the story is the isolation and loneliness of West Indian immigrants in London during that time.
Moses and his loosely banded group of fellow West Indians feel displaced in their new environment, even though some of them have been in London for a number of years. They are on the whole good people who want nothing more than "a little work, a little food, a little place to sleep...(they) only want to get by...don't even want to get on". Yet the characters, who are black, struggle against racial discrimination and economic hardship. Largely "unskilled and semi-educated", they are forced to live "in seedy furnished rooms in run-down areas and have to scramble for what jobs there are or go on the dole".
The immigrants' difficult situation is intensified by the fact that they have cut themselves off from "their roots and traditional means of support", but cannot find acceptance in their adopted home. They exist in a hopeless state of isolation, "lonely" in the city of London.
The story is told in a light-hearted, comic tone, but the sense of emptiness which engulfs the characters' lives is overriding. Laughter cannot completely hide the desperation they feel.