The Lord Chamberlain's requirements were a set of four requirements that theatres in Britain were required to comply with, before a licence for a production could be issued. These were printed in the theatre programmes, so that the audience would be aware of the requirements. In the 1980s they were replaced by requirements applied by the local licencing authority, but the format remained similar.
The items governed by the requirements are
The leaving of the theatre at the end of the performance
That gangways and passages must not be obstucted
Limitation for standees
That the Safety curtain must be shown to operate during each performance
The traditional wording of the first requirement was "The public may leave at the end of the performance by all exit doors and such doors must at this time be open". The slightly obvious & humorous interpretation of this was ephasised by Flanders & Swann in their song in "At the Drop of a Hat" At the Drop of a Hat was a musical review, described by its authors as An After-dinner Farrago. The show consisted only of the two artists, Michael Flanders & Donald Swann, sang & played the piano. ...
References
The programmes of many London Theatres of the period 1948-2000