Bought by Liu Gang, a Chinese lawyer, in 2001 from a book dealer in Shanghai, the map is dated 1418 and shows with remarkable accuracy the whole world — each continent with its correct shape, latitude and longitude. Mr Liu has carried out extensive research to try to authenticate the map, which he plans to unveil to the public in Beijing on Monday.

Gavin Menzies, the British author, contends that the discovery is further proof that Zheng He, a Chinese navigator, and not Columbus, discovered America. Mr Menzies, a former Royal Navy submarine commander, said: “It’s authentic. It supports my book to the hilt.”

He published 1421: The Year China Discovered America in 2002 and the work soon became a bestseller, sparking furious discussion in academic circles in China and beyond. Mr Menzies uses numerous references to maps in his book that relates how the fleet of Admiral Zheng He sailed to Cuba and to Rhode Island in 1421, seven decades before Columbus made landfall in the New World in 1492.

Now he believes that this map, perhaps one that guided the admiral’s ships, will provide new evidence that the fleet first reached the Americas on a 1415-18 voyage. The admiral is recorded as having made seven voyages. Mr Menzies says that he is well aware that if the map were to be proved a forgery it would have catastrophic consequences for his own reputation — not to mention Mr Liu’s. They will have to wait until the end of the month for carbon dating, although experts have said that the map is well over a century old.

Mr Liu, a founding partner of one of China’s largest law firms, had begun to question accepted wisdom about Admiral Zheng He and his voyages after studying his purchase. After reading Mr Menzies’ book last year, the Chinese lawyer, with a background in the City of London, realised that he might not be alone in questioning the achievements of Columbus.

It would seem surprising that among China’s huge archives no records remain to show the admiral — the only Chinese explorer of note — reached the Americas. However, records of his voyages were burnt by later emperors who disagreed with the expansionist policies of Admiral Zheng He’s patron, the Yongle Emperor, who died in 1424.

China, usually swift to hail its triumphs, has been reluctant to take up the theory, even though, if true, it would revolutionise the Chinese contribution to world history.

Zhu Jianqiu, an oceanographer with the Chinese navy and a scholar at the Nanjing Zheng He Institute, said: “In 1421 many maps are mentioned but none of them has anything to do with Zheng He. Chinese scholars cannot share the opinions of Mr Menzies.”

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