New Zealand is mourning the loss of its most revered athlete following the death of middle-distance great Sir Peter Snell. The three-time Olympic champion died in his sleep aged 80 at his Dallas home on Friday.

Snell had been suffering from heart problems in recent years but his wife Miki said he had been leading an active life right up until his death, having made plans to cook a meal after a midday nap.

Snell bestrode the track in the early 1960s, winning gold over 800m in the 1960 Olympics in Rome before bagging a famous 800m-1,500m double in Tokyo four years later. He remains the only man to secure such a double since 1920, underlining his dominance at the time.

The 1960 gold came less than an hour before compatriot Murray Halberg was victorious over 5,000m, with the twin results representing New Zealand’s emergence as an international sporting entity in the eyes of many.

The winner of two Empire Games gold medals, the holder of various world records during his career and never beaten in a major international race, Snell was in 2000 voted New Zealand’s athlete of the century. He was knighted soon afterwards. Ten years earlier, he was the first inductee into the freshly created New Zealand Sports Hall of Fame.

New Zealand Olympic Committee president Mike Stanley said Snell’s impact on his country can’t be overstated.

“His achievements are at the heart of New Zealand’s sporting history and have helped shape our national identity,” Stanley said. “The Golden Hour in Rome 1960 was followed by back-to-back gold medals at the Tokyo 1964 Olympic Games. These incredible races stand out in many Kiwis’ minds as among our greatest sporting achievements.”

Coached by Kiwi athletics legend Arthur Lydiard, Snell was the spearhead of a memorable era in New Zealand athletics. Massive crowds flocked to see him compete against invited athletes around the country.

In January, 1962 in Wanganui, he became the first New Zealander to break a four-minute mile and eclipsed the world record held at the time by Australian great Herb Elliott. A week later in Christchurch, Snell lowered world records for 880 yards and 800m running on grass. Both of those times remain New Zealand records.

After retirement, he studied at the University of California and then at Washington State University, where he gained a PhD. He moved to Dallas to do a post-doctoral fellowship and continue research into exercise physiology.

Snell is said to have enjoyed the relative anonymity of living in the United States but stayed close to New Zealand, where he took some figurehead roles for sports organisations in the 1990s.