So I've been rereading Bernard Cornwell's Sharpe series, and as a Canadian living in the U.S. for most of my life, my experiences with British history have been somewhat lacking due to the American school system. Essentially, I hear lots about the Horse Guards, and how they are supposedly in control of the army. But other times, it's the politicians, and when I went to Wikipedia to try and figure it out, I learn the Horse Guards were a noble cavalry regiment. So, what are the Horse Guards? Thanks for the help!
Horse Guards is a building that hosted the Commander-in-Chief of the Forces and his staff. It still stands just off Whitehall, close to St James and Buckingham Palace. It is to the staff of the building that Sharpe/Cornwall are referring, and especially the C-in-C of the era, the Duke of York (immortalised in song as the chap who led ten thousand men up a hill, etc.)