Mr Davis now believes "the Earth is flat and horizontally infinite - it stretches horizontally forever".

"And it is at least 9,000 kilometres deep", he adds.

James McIntyre, a British-based moderator of a Flat Earth Society discussion website, has a slightly different take. "The Earth is, more or less, a disc," he states. "Obviously it isn't perfectly flat thanks to geological phenomena like hills and valleys. It is around 24,900 miles in diameter."

Mr McIntyre, who describes himself as having been "raised a globularist in the British state school system", says the reactions of his friends and family to his new beliefs vary from "sheer incredulity to the conviction that it's all just an elaborate joke".

http://news.bbc.co.uk/2/hi/uk_news/magazine/7540427.stm