The details of 16 million of Britain's Victorian ancestors have been released online for the first time today.
The 1841 census - the first to record information about individual households - has been published online by Ancestry.co.uk after a deal with the Public Records Office.
It took months of poring over and transcribing what were previously considered unreadable documents. One in 10 of the entries were written in pencil.
The 1841 census is the first under Queen Victoria's reign. The whig prime minister Lord Melbourne had just resigned after being defeated on his attempts to reform the Corn Laws.
His household details, as well as those of his successor Robert Peel, are all available on the site.
All this not is just of interest to history anoraks. Searching for distant relatives is now big business. Genealogy is second only to pornography in generating internet traffic.
When the 1901 census was launched five years ago there were 150m hits, crashing the Public Records Office site.
Ancestry.co.uk says it can cope with such numbers. It already attracts more visitors than Apple iTunes.
The Guardian's Victor Keegan provides a guide to searching for your relatives on be web - what he describes as one of the "great online sports".
