A Bottle Oven

This is a Bottle Oven. A type of kiln. The "bottle" refers to the shape of the structure and not to the kiln's products. This particular one is at Middleport Pottery where Channel 4's  "The Great Pottery Throw Down" takes place.
The metal bands or "Bonts" are there to strengthen it as it expands and contracts with the heat. There would have been more and if you look closely you can see the marks where they were.
At the peak of pottery making in Stoke on Trent there would have been around 2000 bottle ovens. They were originally coal fired and the 1956 Clean Air Act led to the closure of hundreds of potteries in Stoke on Trent.