THOUSANDS of people logged on to the 1911 Census yesterday, stared at the screen for two minutes and then ran from the room with a look of sickened horror.
Henry Brubaker, of the Institute for Studies, said many had hoped to find they were the descendants of a passionate but doomed romance between an East End match girl and the Duke of Clarence.
Instead thousands have discovered they are the mutant progeny of an illegal union between a slack-jawed farm labourer and his mentally retarded sister.
Carys Hughes, an office worker from Bedford, said: "I was really interested in my great grandparents on my father's side as, for some reason, we were never allowed to talk about them when I was growing up.
"When I logged on I soon discovered that great grandma's maiden name was the same as her married name.
"Sure enough, after a bit more research, it all became horrifyingly clear."
Hughes added: "I suppose now they'll have to take away my driving licence and put me in a home.
"Still, at least they were married. It would be so embarrassing to find out that you're the bastard offspring of sibling incest."
Professor Brubaker said the 1911 Census may be repulsive but it would give us a much deeper understanding of modern British culture including the Daily Mail, the Labour Party and Sky One's Are You Cleverer Than a Bag of Tomatoes?