Image copyright NASA Image caption Tecwyn Roberts (seated) with Glynn Lunney in mission control

The grainy black and white images of Neil Armstrong's giant leap on the moon are a defining moment in human history.

Yet the millions who watched live - and ever since - on TV, have a Welsh engineer from a tiny village on Anglesey to thank.

Tecwyn Roberts was instrumental in the Apollo missions as chief of Nasa's network engineering division.

"We couldn't have done the landing without him," said former director of the Johnson Space Center, George Abbey.

He added: "Tec was responsible for all the communications that we had, the television we saw, the data that came in and he had to make sure it happened and happened the right way. I'm very proud of him."

Image copyright Getty Images Image caption An estimated 650 million people watched the moon landing live on TV

Born in Llanddaniel Fab in 1925, Tecwyn was educated on Anglesey where he took up an engineering apprenticeship after school.

After briefly serving with the RAF during World War Two, he studied aeronautical engineering at the University of Southampton before taking a job with an aircraft manufacturing company in Toronto, Canada.

When the programme he was working on was suddenly cut, he followed many of his colleagues to join Nasa's recently created space task group at Langley Research Center in Hampton, Virginia.

The aim of Project Mercury was to put a man into Earth's orbit and return him safely.

Appointed as Nasa's first flight dynamics officer, he rose through the ranks and in 1964 was put in charge of the network of tracking stations to support the manned space flight programme.

Image copyright NASA

By the time of the first landing on the moon, Tecwyn was chief of the network engineering division and awarded the exceptional service medal by Nasa.

Former Nasa flight director and director of the Johnson Space Center, Christopher Kraft, was instrumental in establishing the agency's mission control centre.

He said: "Tec really knew what the hell he was doing. I feel like I was damn fortunate to have that man in my pocket.

"He was like a brother to me; a little better. People like Tec Roberts, who you could trust implicitly and know that were going to do a good job, were rare and he was one of those and I thank him for it and I don't think he ever got the credit."

Elected as a fellow of the American Astronautical Society and having been honoured with the award of merit by Goddard Space Flight Center, he retired in 1979 and died in 1988 in Crownsville, Maryland, aged 63.

Image caption Tudur Owen has been investigating the role a "gifted Welshman played in mankind’s greatest achievement"

Glynn Lunney, former flight director on Apollo programmes, who started as an apprentice under Tecwyn, said: "Tec was a man that was easy to like, he was gentle and we loved him.

"One of the things that struck me very quickly about Tec, he was positive about things, positive about finding solutions, he didn't get uptight about things.

"All 22-year-olds ought to have a couple of years working for a guy like Tec. If they got that, then they were fixed for life."

Rocket Man: NASA's Welsh Hero is on BBC One Wales at 22:35 on Thursday 18 July and on the BBC iPlayer.