The official residence and office of the british monarch is westminster abbey buckingham palace windsor castle tower of london

The official residence and office of the British monarch is Buckingham Palace.

Explanation:

Buckingham Palace is the official residence of the British monarch in London. It is also used for official ceremonies, state visits and sightseeing. It is famous for hosting a substantial part of the Royal Collection, an extraordinary collection of artistic works resulting from real collecting. The palace is a meeting point for the British in times of crisis and festivity.