England was technically an empire up until the 1950s. start with the "protestant wind' and "Spanish Armada's when doing research. This dates back to the late 1500s when England replace Spain as the major power in Europe at the time.
Also , note that England had control over southern Africa, parts of the middle East, Egypt, india, parts of Asia including Hong Kong, Canada prior to independence, USA prior to independence, and always fought for supremacy in Europe between France up until the 1900s.