A medieval re-enactment society in Sweden claims to have solved the mystery of an American who awoke in a California motel room earlier this year insisting his name was Johan Ek and communicating only in Swedish, despite an ID card naming him as US-born Michael Boatwright.

Members of the Swedish branch of the Society for Creative Anachronism, however, knew him by yet another name: Strongbow, a keen participant of the group's jousting team.

"He was pretty good at jousting - one of the better performers," SCA member Johan Cassel told The Local, an English-language Swedish news website.

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The American lived in Sweden in the 1980s, Mr Cassel said, where he picked up the language. "He could speak pretty good Swedish, although you could hear that he came from an English-speaking country. He had an accent," he said.

Mr Cassel also recalls 'Strongbow' being friendly with a man called Ragnvald Göransson Ek, so speculates that was where the name 'Johan Ek' came from.

Mr Boatwright, 61, was found unconscious in motel room in Palm Spring in February. Doctors at the hospital treating him say he is probably suffering from a condition known as Transient Global Amnesia, a disruption to the short-term memory.