The first is The Banquetting House, which was built in the eartly years of King Charles I reign, and the ceilings are all by Rubens in honour of King James I ... and the sovereign rule of kings. It became, sadly, more famous later in King Charles reign as the place where a scaffold was built, and he was beheaded there.
Amazingly some years later most of London was destroyed by fire in 1666, but King Charles II managed to save the building by blowing up buildings around it ... and then during the Blitz of WWII it survived ....
The other B, is The British Library ... you can register and request to see any books of the millions they have stored in the vaults. However, there are some books, and documents that are on display ... including one of the copies of the 1215 Magna Carta, as well as the Papal Bull annulling it!
Charlotte Bronte - and, yes, it is impossible to read it is so tiny
Welsh Laws 1596
Portolan Chart 1470 - an early Sat-Nav
The Lindisfarne Gospels, made in 700AD
The Gutenberg Bible, made in 1454 and the start of modern printing