One small step for man, one giant leap for mankind: a still from TV footage showing Neil Armstrong's first step on the moon Photo: NASA

Obama Photo: AP

Gary Peach, 73, who was working at a Nasa space tracking facility in Australia in July 1969, says that he coined the phrase because he feared that the landmark moment would pass without a suitably dramatic opening line.

He said that he worried that astronauts would mark mankind’s arrival on the moon with a mundane observation about dust.

After toying with variations on the theme of taking steps, he says that he came up with the phrase: “That’s one small step for a man; one giant leap for mankind”.

After suggesting it to his director, the next he heard of it was when Neil Armstrong famously fluffed the line, failing to pronounce the “a” audibly as he set foot on the moon.

Mr Armstrong says that he came up with the phrase himself as he stepped off the lunar module but has spoken in the past about drawing on thoughts which were there “subliminally or in the background”.

Mr Peach, a grandfather of four who trained as an engineer during national service with the RAF in the 1950s, described the fact that he has never hitherto been credited with coming up with one of the most quoted phrases in history as a minor “annoyance”.

He claims that he only spoke openly about it after being drawn into discussion about the moon landing in an internet forum.

It was during final preparations at the Tidbinbilla tracking station near Canberra for the moon mission in July 1969 that he hit on the term, he maintains.

“It was already a topic had been among the boys anyway,” he said.

“I was thinking, what is he going to say when he steps down on the moon for the first time? It is going to be in the history books forever – it will probably be something like ‘Holy **** look at all that dust’.

“First of all I crafted it as ‘it’s a small step for a man, it’s a big step for mankind’ and then I thought I have too ‘steps’ in there so I changed it to a leap.”

A few days later he passed his idea to the director of the station in a chance conversation as he made some late night checks as the mission was due to get under way.

“He asked me have you any other concerns and I said: ‘Yes, what they are going to say’,” he recalled.

Mr Peach believes that the director then passed on his suggestion to mission control and the next he heard was as Mr Armstrong stepped onto the moon.

Even when the astronaut garbled the line, he says that he was not displeased.

“I was busy working, it didn’t really matter, I didn’t really give it a second thought,” he said.

Speaking in 2001, Mr Armstrong said that he came up with the phrase as he waited in the Eagle landing craft before finally walking on the moon.

“I thought about it after landing,” he told a Nasa history project.

“Because we had a lot of other things to do, it was not something that I really concentrated on but just something that was kind of passing around subliminally or in the background.”