The current court is the successor to courts pre-dating the County Courts Act 1846, which introduced the modern system of county courts. The 1846 Act deliberately did not extend to the City of London and so did not alter the position of the Mayor's Court and the City of London Court, although later legislation applied the rules prevailing in county courts to these two courts as well. The two courts were combined with effect from 1 January 1921 by the Mayor's and City of London Court Act 1920, as commemorated on a tablet by the court entrance.
In 1971, the old Mayor's and City of London Court was abolished (by section 42 of the Courts Act 1971), the City of London was made a county court district and the new county court for the city of London was given the name of its predecessor. It remains the only county court not to contain "county" in its title.