A population census is a head-count of the population of a country on one particular night

The first UK census was established in 1801and a census has been taken every 10 years since then, except in 1941 when the country was at war

The early census returns from 1801 - 1831 do not contain much personal information as they were simply population counts. Most were later destroyed

The 1841 census gives details of name, age (but only within 5 years for those over 15), occupation and whether born in the county in which then living or in Ireland, Scotland or abroad

The 1851 - 1901 censuses give details of relationship to head of household (e.g. son, servant), condition (e.g. married, widow), age, occupation, birthplace, and from  1891, whether employer or employee

The 1911 census gives further detail and is being released early in phases, with the exception of 'personally sensitive information'