Lucas, the son of an engineer, was born at Greenwich and graduated from Cambridge University, where he was elected a fellow in 1904. In 1914 he joined the research department of the Royal Aircraft Establishment, Farnborough, and while carrying out his duties died in a midair collision.

In 1905 and 1909 Lucas published two papers that clearly stated the all-or-none law of nervous stimulation: a stimulus can evoke a maximum possible response or nothing. If stimuli of varying strength appear to elicit responses of increasing contraction this is because, Lucas demonstrated, more nerve fibers are responding rather than that the same number of fibers are reacting with greater vigor.

Lucas's work became more widely known through its later development by his youthful collaborator, Edgar Adrian.