All-in professional wrestling was a hybrid combat style that gained immense popularity in the United Kingdom during the 1930s. Combining traditional catch-as-catch-can techniques with theatrical showmanship, the format was originally marketed as a "no holds barred" legitimate contest. However, as the decade progressed, the industry shifted toward increased violence and sensationalism, leading to legal bans and a decline in prestige. To restore order and legitimacy after World War II, officials introduced the Mountevans rules, which formally replaced the chaotic "all-in" era. Despite this official rebranding to modern freestyle, the term persisted in British pop culture as a colloquial, and sometimes mocking, label for the sport.