The Chinese authorities have moved swiftly to airbrush from history the popular myth that the Great Wall is visible from space.

Schools textbooks face immediate revision after the country's first astronaut confirmed that - after 21 hours in orbit - he had been unable to spot the monumental structure.

"The scenery was very beautiful," said Yang Liwei. "But I didn't see the Great Wall."

This is not the end of the matter. US astronaut Gene Cernan is quoted in the Singapore's Straits Times as saying that "At Earth orbit of 160km to 320km high, the Great Wall of China is indeed visible to the naked eye".

Cernan reckons Yang simply wasn't trying. He said: "If you know where to look and you look hard enough, you can also see the Astrodome in Houston, Texas, where I live."

Incredible. You didn't spot any WMDs while you were up there, did you, Gene? ®