How spontaneous was Neil Armstrong's famous moon landing line?

Neil Armstrong on the Moon with Buzz Aldrin (AP)

"That's one small step for [a] man, one giant leap for mankind."

For years the consensus among space historians and astronauts has been that Neil Armstrong, who died last year age 82, came up with this line after arriving on the moon, as part of the first moon landing mission in July 1969. However, in a fashion that will be familiar to sibling rivals everywhere, Neil's brother Dean Armstrong has recently come forward to nab part of the credit.

He told the Telegraph that Neil Armstrong ran the quote by him for approval as they played the board game Risk in the Cape Canaveral, during the months before the launch.

Space historian Robert Pearlman is not happy: "Whether intentional or not, Dean Armstrong's account no suggests his brother has been lying for 40-plus years," he said.