Why British carrier aircraft carried observers

Why did British naval aircraft carry observers and navigators?

A separate navigator allowed the pilot to concentrate on flying while the crew found its way over the sea at night with limited navigation equipment.

Flying at night demanded sustained attention even before enemy fire and harbour obstacles complicated the task. Requiring the pilot to navigate at the same time added another difficult job. Observers worked with a compass, ruler, protractor, pencil and their own calculations. A watch also helped them interpret the carrier's beacon. A separate navigator allowed these duties to be divided during long flights with the equipment available in 1940.