A historian has debunked the legend surrounding Britain's most distinguished war medal, saying the metal used to cast the Victoria Cross comes from two cannons captured in China, and not, as widely believed, from Russia.

John Glanfield, author of a recently published book that examines the origins of the Victoria Cross, says new evidence points to the cannons being captured by Anglo-French forces in a battle for the Taku forts near Tianjin in 1860, one of the last battles of the second opium war.

That contradicts the long-held belief that the cannons were captured in battle against the Russians at Sebastopol in 1855 during the Crimean war.

Glanfield has told Victoria Cross experts of his findings and they are "absolutely amazed that at last we've been able to cast this light on a tremendously strong legend - that they came from Russia".

He was somewhat surprised himself, because while he and a few other experts knew the cannons were actually Chinese, "the presumption was that the Russians must have captured them in some earlier Sino-Russian war".

The Victoria Cross is the highest honour awarded to British and Commonwealth soldiers for valour "in the face of the enemy".

In Glanfield's book - Bravest of the Brave, the Story of the Victoria Cross, published in December - he wrote that there was no evidence showing the two cannons came from the Crimean war, although he was not able to pin down the origins by the time of publication. But he continued his research and in the past few weeks found evidence pointing to their Chinese origins.

In his book, Glanfield also cites research showing a third, mystery cannon was used to make the cross from its creation in 1856 until it was used up in 1914, when the armoury started using the two Chinese cannons.

There is compelling evidence, Glanfield said, that the two cannons - now stored at the Royal Artillery Museum in Woolwich, London - were captured by an 18,000 strong Anglo-French expeditionary force. The troops, on their way to Beijing, had sailed up the Hai estuary and on August 21, 1860, attacked the formidable Taku forts guarding the river. A lucky shot took out the fort's ammunition dump.

The troops continued on to Beijing, infamously looting the city, and burning down the Summer Palace and Old Summer Palace.

A year later, 200 to 300 Chinese cannons captured in the battle arrived by ship at Woolwich arsenal, according to a contemporary news report that Glanfield found, which also featured drawings of captured weaponry resembling the two cannons.

The arsenal had also received a big shipment of captured Russian weapons in 1857. Captured cannons were typically melted down to make new weapons, but Glanfield said Russian metal was preferred.

"I'm afraid to say Chinese cannons were dangerous. The Chinese metal carried impurities, and those impurities made it of less strength," he said.

Therefore, it is highly likely only the Chinese cannons were left by 1914, when the order came down that more metal was needed for the Victoria Cross.

Arsenal staff probably mistakenly assumed that the cannons they chose were Russian, he said.

"The fact is those two guns, in all logic, can only have come from the Taku fort action."

He plans to publish his findings in a specialist journal.