One of the greatest days in the star-studded career of Sir John Walker now comes with a big "what if?"
On August 12, 1975 - August 13 NZ time - Walker set the record for the mile in the Swedish port city of Gothenburg, smashing Tanzanian Filbert Bayi's mile record of 3m 51s and breaking, said Peter Snell, the last mythical barrier for milers.
But what if he'd picked another race on a faster track to break the record? What if he'd received more sophisticated pace-making?
"I could have run in the 48s, maybe low 48s," Walker said.
His record-breaking campaign was a world away from the scientific, detail-driven efforts of today's athletes. By contrast, Walker's decision to try to break Bayi's record was arbitrary.
"I'd run 19 races in Europe and won 19 races and had run very fast times yet felt like I hadn't achieved anything," Walker recalled. "I got frustrated and basically said to the promoter in Gothenburg that I wanted to go for the mile record and could he change it from 1500m, which he did."
In contrast to the trends of the day, Walker eschewed speed work and spent the two weeks beforehand racking up mileage - 90 miles (145km) one week, 85 the next - before tuning up with an 800m race in Helsinki.
Sustenance on the big day took the form of a fish and chip lunch washed down with Coke.
"We didn't worry about diet, we just had to survive," Walker said of the New Zealanders' lifestyle on the European athletics circuit.
"We raced far too much, we had to. We were pioneers."
Gothenburg was windy that night, not conducive to fast times, but if that was a handicap it was nothing compared to the inexperienced pacemaker, local lad Goran Savemark.
"The pacemaker was pretty lousy. He ran the first lap too quick then stepped off the track with 700m to go and left me to it."
That Walker ran a faster time, 3m 49s flat, five years later, when he was past his peak years, has him convinced he could have gone a lot faster if the race had been planned better, and that he could have lowered the record to the high 3m 47s if he had focused on it.
"I had a different attitude to the other runners.
"My attitude was to run to win and let time take care of itself. I probably regret that a little bit now," Walker says.
"I only ever had one go at the world record and once I had it I never had a go again."
Even given Walker's regret, his performance was universally lauded.
"It's a time we've all dreamt of," Snell said at the time.
"The mile will never be run in 3m 40s so Walker has knocked off the last mythical barrier."
"He was correct," Walker says.
Even now, when Hicham El Guerrouj, 11 years ago, lowered the mark to 3m 43.13s?
"You can never say never, but I think 3m 43s is over the top. They're actually getting slower. They're not going any faster now, they've stopped going fast for some unknown reason," Walker says with barely concealed scepticism.
Walker's record has long been broken, by Sebastian Coe at Oslo in 1979.
"I was actually in the race. It made me pretty despondent. I mean in Norway I was introduced as the world record holder and four minutes later I was nobody. Nobody cared," Walker says.
And this time, for a man who got so many things right, he is absolutely wrong.
As Coe said so evocatively in Auckland two years ago: "He was athletics' first superstar. John caught the moment. It was his looks, his talent - it was just a great, great moment for our sport."
* 3m 54.5s - Herb Elliott (Australia), 1958, Dublin
* 3m 54.4s - Peter Snell (NZ), 1962, Wanganui
* 3m 54.04 - Peter Snell (NZ), 1964, Auckland
* 3m 53.6s - Michael Jazy (France), 1965, Rennes
* 3m 51.3 - Jim Ryun (USA), 1966, Berkeley
* 3m 51.1s - Ryun, 1967, Bakersfield
* 3m 51s - Filbert Bayi (Tanzania), 1975, Kingston
* 3m 49.4s - John Walker (NZ), 1975, Gothenburg
* 3m 48.95s - Sebastian Coe (UK), 1979, Oslo
* 3m 48.8s - Steve Ovett (UK), 1981, Oslo
* 3m 48.53s - Coe, 1981, Zurich
* 3m 48.40s - Ovett, 1981, Koblenz
* 3m 47.33s - Coe, 1981, Brussels
* 3m 46.32s - Steve Cram (UK), 1985, Oslo
* 3m 44.39s - Noureddine Morceli (Algeria), 1993, Rieti
* 3m 43.13s - Hicham El Guerrouj (Morocco), 1999, Rome