Maybe it was the brilliant mind.
Or the fascinating mix of big-hearted athlete and elite medical student.
Perhaps it was the humble upbringing.
The little New Zealander that could, running in the famous black singlet with a silver fern on the chest. That always gets me.
The sport: Athletics
The event: Olympic Games 1500m final
The place: Berlin, Germany
The date: August 6, 1936
Most likely, it was simply the story he had to tell that engaged my interest in Jack Lovelock and led to a long-time fascination with one of New Zealand's greatest runners.
I first encountered the legend of Lovelock when I read James McNeish's remarkable work of "faction", Lovelock, which uses a blend of historical fact, assumptions and imaginary encounters to paint the picture of an athletic superstar whose rise to glory was paved with the bricks of obsessive perfectionism.
Lovelock was a kid from Fairlie, the son of an English immigrant who learned to run - with wings on his heels - as a boarder at Timaru Boys High School.
Education, in medicine, followed at the University of Otago, after which he won a Rhodes Scholarship and entered the rarified air of Oxford and a glorious era (1930-36) of middle-distance running.
That's when I see Lovelock's story unfolding in my mind.
I see Lovelock rubbing shoulders with the toffs at Oxford, the colonial in an upper-class world, mocked for his antipodean twang at the same time as he is admired for his unstoppable feet.
I see him hunched over his diary, scribbling his latest theories on fitness and nutrition, and I see him staring out at the spires on the nights he cannot sleep.
I see Jack breaking the British Empire record for the mile in May 1932, then struggling in the Olympic Games in Los Angeles, finishing only seventh in the 1500m final.
I see our boy rebounding a year later to break the world mile record, and winning Empire Games gold a year after that.
I see the first "Mile of the Century" at Princeton in 1935; Lovelock easing the pain of an inflamed knee by injecting "Flem's juice" - an experimental vaccine cooked up by Alexander Fleming - and I see the wry New Zealander outrunning the greatest field in middle-distance history.
Most of all, I see Berlin.
To a backdrop of Hitler and swastikas and propaganda and, again, a phenomenally strong field of runners, I see a black singlet and wavy blond hair, and I hear Harold Abrahams' famous, passionate commentary ("Come on, Jack! My God, he's done it! Jack, come oooonnnnn!).
I see Jack's perfect race.
I see a man daring to sprint from as far out as 300m against Cunningham and Beccali and the rest of the great stars of the track.
I see a man winning New Zealand's first Olympic gold medal in athletics in a world record time of 3min 47.8sec.
And I wish I'd seen it.