The first ever designed office building in London, the Admiralty (also known as Ripley Building for its designer Thomas Ripley) was built in 1726 for a now-defunct organisation called, appropriately, the Admiralty. It's amazing how they come up with this stuff. Anyway, the Admiralty served the authority in charge of the Royal Navy, which is just what you'd expect from an organisation called the Admiralty. The U-shaped building contained a board room, state rooms, and apartments for the Lords of the Admiralty. This allowed those lucky prancing lords to live and work from home, probably doing absolutely bloody nothing, making them very much the freelance web designers of their day.
By 1759, the city had widened the street in front of the Admiralty, which cut into their courtyard. The Lords of the Admiralty commissioned a new façade to run along the street - the Admiralty Screen, as it's called, is still there today, hiding the dull administrative building behind it with Greek classicism. My least favourite kind of classicism.
In 1964, the Admiralty became the home of the newly established Department for International Development. I have no idea what what is, because I fell asleep just typing its name.