The Licensing Act of 1737 was a pivotal moment in theatrical history. Its purpose was to control and censor what was being said about the British government through theatre. The act was modified by the Theatres Act 1843 and was finally repealed by the Theatres Act 1968.
The British parliament, as well as the king, felt that the act was necessary. At the time, theatre was open source in terms of content, although there were laws that were not strictly enforced. People had free rein to say anything they wanted through theatre, and in this case, that included all their troubles with the government. The free speech of theatre posed a threat to the government, as this opened doors for revolutionist to spread their beliefs and opinions to the masses without concern of the government intervening. This concerned politicians since with no censorship the people could ridicule and plot against their own government without recourse.
While the government was concerned, there was no legitimate need for a censoring act at the time prior to 1737. So during a 4-year period between 1733 and 1737, the government had to wait until there was a need for the act to be created.
Through this act the government was able to control and censor theatre with much more force than any single law that existed beforehand. Previous laws, though official, were not strictly enforced.
The function of censorship of plays for performance (at least in London) fell to the Master of the Revels by the time of the reign of Queen Elizabeth I. The power was used mostly with respect to matters of politics and religion (including blasphemy). It was certainly exercised by Edmund Tylney, who was Master from 1579 to 1610. Tylney and his successor, George Buck, also exercised the power to censor plays for publication. The Master of the Revels, who normally reported to the Lord Chamberlain, continued to perform the function until, with the outbreak of the English Civil War in 1642, stage plays were prohibited. Stage plays did not return to England until the Restoration in 1660. During the creation of the Licensing of 1737, Robert Walpole was the standing Master of the Revels