Fun fact: While they were the monarch of the British Empire, they weren’t styled the British Emperor. Edward VII for example was King of the United Kingdom of Great Britain and Ireland, the Dominions and Emperor of India.
In any case:
Regency era. See Napoleonic Wars. Colonization everywhere, with territory won and lost in wars and a king that lived a long, long time as an absolute madman. The ‘regency’ is the crown prince being appointed to run things because George the III is bonkers.
Victorian Era was 1837 to 1901, arguably the highest point of the Empire’s power and for most of it England was the wealthiest nation on Earth. With the defeat of Napoleon England has unquestioned dominance of the sea. A relatively popular monarch manages to ride out the 19th century without England getting into the revolutionary business.
Edwardian era. 1901 to 1910. A golden age. King was generally considered competent, but his mother lived and ruled so long that he was 58 when he took the throne. A golden age, especially compared to what comes next. England’s rich and prosperous and it’s good to be a upper class person. Reviews are mixed for everyone else.
There has never been a British/English emperor, the idea was suggested, last time in 1801 with the union of Great Britain and Ireland but George III declined and remained the king of “the United Kingdom of Great Britain and Ireland”
British monarch from 1876 to 1948 was alos the Emperor of India. Even if this period overlaps in part with the Victoria (1837-1901) era the name is from hers as a Queen, not an Empress.
The Regency era is commonly c 1795-1837 and the Elizabethan era 1558-1603, neither was when the Monarch was also an emperor/empress.
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