Many reporters just love this expression; they use it all the time. Any time the top people of an organisation are present during a press conference, the reporter says/writes that it was attended by the `top brass’. The expression is considered to be informal, and is mostly used in British English.
Example: The minister has said that there will be a reshuffle of the army’s top brass.
The expression `top brass’ was first used in the Army. `Brass’ referred to the gold braid found on the hats of military officers — it indicated the individual’s rank. The word `brass’ is actually a shortened form of `brass hat’, and this was the term used by enlisted men in the late 19th century to refer to their commanding officers. It was during World War II that `brass hat’ became `top brass’. As time went by, the expression began to be used in non-military contexts; important individuals of an organisation began to be called `top brass’. The term `the brass’ can also be used to refer to such people.