Leonard Street was a street in Shoreditch.
Ram Singh cut through it on the way from Great Eastern Street to Swallow Avenue. (PROSE: Joyride)
Behind the scenes
Although not stated in the novel explicitly, it can be inferred that Leonard Street is in Shoreditch because Ram's body goes from 1 Wellington Road, which is in Shoreditch to Swallow Avenue, which is also in Shoreditch via Leonard Street.