on some of the intervening fifth anniversaries. The first four censuses (1801–1831) were mainly statistical: that is, mainly headcounts, with virtually no personal information. A small number of older records exist in local record offices as by-products of the notes made by enumerators in the production of those earlier censuses; these might list all persons or just the heads of households. The 1841 Census was the first to intentionally record names of all individuals in a household or institution. The first simultaneous census of the British Empire, covering the United Kingdom, India and the Crown Settlements, took place in 1881. The Census Act 1920 provides the legal framework for conducting all censuses in Great Britain (Scotland, England, and Wales). The primary legislation for Northern Ireland was introduced in 1969. Before this legislation, it was necessary to have a separate act of parliament for each census. Britain was also responsible for initiating and co-ordinating censuses in many of its overseas colonies. Because of the disruption caused by the Second World War, there was no census in 1941. However, following the passage into law on 5 September 1939 of the National Registration Act 1939, a population count was carried out on 29 September 1939. The resulting National Register was later used to develop the National Health Service Central Register. Censuses were taken on 26 April 1931 in Great Britain, but the returns for England and Wales were destroyed in an accidental fire during the Second World War. On 24 April 1966, the UK trialled an alternative method of enumeration – long form/short form. Every household was given a short form to complete, while a sample of the population was given a long form to collect more detailed information. The short form was used for the population count and to collect basic information such as usual address, sex, age and relationships to other household members. This was the first and only time that a five-yearly census was carried out in the UK. Release of information England and Wales The British government undertakes the census for policy and planning purposes, and publishes the results in printed reports and on the website of the Office for National Statistics (ONS). A number of datasets are also made available. Public access to individual census returns in England and Wales is normally restricted under the terms of the 100-year rule (Lord Chancellor's Instrument no.12, issued in 1966 under