
I want one too, not because I am a follower of George IV, but because the teapot is just plain cool. This teapot has no lid. There is no apparent way to fill it.
The way it works is this: If you invert the teapot you see that running up into the pot from the bottom is a tube. You fill the pot through the tube, turn the pot rightside up and the water.....aaaah, too hard to explain. Look at this glass version of the pot and you can see how it works.

You can look for antique Cadogan pots (like the top photo) manufactured by the Rockingham works in England or you can buy the modern glass version shown here (called the Mystery Pyramid Teapot) for $30 from a site that also sells Klein bottles.
Just in case you don't know what a Klein bottle is, it's a bottle that, like a Moebius strip, has a continuous surface. Enough said. You can check out the Klein bottle site to learn more.