The Lord Chamberlain's requirements were a set of four prerequisites for a licence for a production in British theatres. These were printed in theatre programmes so the audience could be aware of them. In the 1980s, they were replaced by similar requirements applied by a local licencing authority.

They cover:

1. Leaving the theatre at the end of the performance.
2. Freedom of gangways and passages from obstruction.
3. Limitations on standees.
4. Operation of the safety curtain 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 humorous interpretation of this—that the public could leave through closed doors or/and they are locked in the auditorium until the close of the performance and that they can't leave early—was addressed in song form by Flanders and Swann in their musical revue At the Drop of a Hat.

References

Many London theatre programmes, from the period 1948–2000