Answer:
a population explosion due to better farming methods.
Step-by-step explanation
The creation of better farming methods makes the number of job opportunities and food availability become located in the cities.
Knowing this, a large portion of Britain population decided to move to the cities in order to get a shot at a better standard of living. Ironically, since most people think that way, it instead created a population explosion that resulted in a large number of unemployment and poverty in the cities.