Field of the Forty Footsteps
At the back of the British Museum, once called Southampton Fields. The tradition is that two brothers, in the Duke of Monmouth's rebellion, took different sides and engaged each other in fight. Both were killed, and forty impressions of their feet remained on the field for many years, where no grass would grow. The encounter took place at the extreme north-east of Upper Montague Street. The Misses Porter wrote a novel on the subject, and the Messrs. Mayhew a melodrama.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894