Henry Oliver—Galahad—is the character who best represents loneliness in The Lonely Londoners. His experiences create more isolation with every unmet expectation and the resulting loneliness is underscored by the excitement and optimism he had when he arrived in London.
Galahad arrives in London optimistic but ultimately unprepared for the realities of life in the city. This is shown when he arrives in clothing that is not appropriate for the weather. He has illusions about the city and his life there that are not realistic—mainly that he will be economically and socially successful. He expects an idealistic life but is unable to achieve it despite his personal goodness.
When Galahad goes on his date with Dolly, they are unable to understand how the other one acts. Despite Galahad being on his best behavior, he is unable to impress her. She, in turn, is not what he expects from a woman in London. She is gauche and has little class. The resulting sense of isolation creates more loneliness than would usually stem from a failed date.
As The Guardian points out, the isolation is highlighted again near the end of the book when Galahad is starving and tries to capture and eat a pigeon. A woman stops him, saying that she will call the police if he does not desist. The gap between Galahad's expectations and the reality of London is highlighted here. From one view, a man chases an animal to feed himself when he has nothing else. From the other, a woman stops a man from attacking an animal in a park. The two experiences belong to different cultural and social spheres and cannot coexist.
Ultimately, one of the reasons that Galahad echoes Moses's sense of loneliness is because The Lonely Londoners explores Moses and his life in London through Galahad's experiences as a new arrival. As Moses shows off London to Galahad, it underscores the sense of loneliness that the city provides to all the characters. Galahad's optimism slowly wanes throughout the book as he tries and ultimately fails to fit into a society that will not accept him.