I want to know the answer to the following question:
In what century did the habit arise of pubs selling beer from only one brewery?
All the background I'm provided with is that "After the development of the large London Porter breweries in the 18th century, the trend grew for pubs to become tied houses which could only sell beer from one brewery (a pub not tied in this way was called a Free house).". Is that enough to answer the question?
Answer: yes