Longtime seat of the British Empire and capital of the United Kingdom. It lies astride the River Thames 50 miles (about 80 km) upstream from its estuary on the North Sea. It has burned and been rebuilt several times, notably in revolt of Queen Boudicca in 60 CE and in the Great Fire of 1666. It became a large trade center in the Middle Ages and expanded rapidly during the 16th and 17th centuries and during the Industrial Revolution. During World War II the city was heavily bombed. London is not to be confused with Greater London which refers to all 32 London boroughs (Inner and Outer London boroughs) and the City of London; London is used to refer to the 12 Inner London boroughs and the City of London.