If you’re trying to find a long lost relative, are investigating the British government’s reforms to combat the post-WWI economic depression, or are researching cases of 16th century infanticide, you may well find what you’re looking for at The National Archives in Kew.
This government-run agency holds over a thousand years’ worth of documents dating back to the time of the Domesday Book to the present, including court documents, correspondence between ministers and government departments, census and Home Office records, and birth, marriage and death certificates. There is a wealth of information available on their website, but if you can’t find what you need on their online catalogue you can visit their vast archive location free of charge provided you take two forms of ID.