Ever since the Bathurst 1000, Australia's greatest motor race, ended at about 4.30pm local time last Sunday - in nice time for the opening laps of the Japanese Grand Prix - I've been wondering exactly why I found it, lap by lap, so mesmerising for all those hours.
Normally I'm not good with distance races. The circuits tend to be big, the cars disappear for long periods and rarely dice, quite soon into the event each car starts having its own race, and after an hour or two true appreciation of what's going on is left to the competitors and teams, or a relatively few true students of the formula.
Not so at Bathurst. The race may last seven hours but it goes in several different phases that make the time fly and never let the tension ebb. First there's the spectacular nature of the circuit: drive it at 40mph in your hire car, and you simply have no idea how they do it. No Herman Tilke could ever design a 3.2 mile circuit like this one, with its huge straight that takes you to the rev-limiter in top and its complex of quick, blind bends that also rise and fall and are usually flanked by concrete walls.
Then there are the cars themselves, 1400kg, 550bhp machines - bulky with it - that share many key components (space frame, rear suspension, transaxle, running gear and very little that could be called electronic) which makes the fastest cars very similar in performance. They're quick but don't develop much downforce, so speeds nowadays exceed 190mph at the end of the mighty Conrod Straight, where cars head into a scary right-handed kink called The Chase without a lift.
Finally there are the drivers. The locals consistently wipe the floor with the very best imports, and almost always have, simply because, as at the 'Ring or Spa, local knowledge counts for everything when you're competing in an equal car.
Best of all, competition is so close. With 20 laps to go this year, the top five contenders were visible in the same TV frame, with several others not far away. The winner for Ford this time (by a few tenths) Mark "Frosty" Winterbottom, has been racing his friend, second-placed Holden driver Jamie Whincup, all his life, but Whincup had been the more successful by a long chalk. Winterbottom, needing redemption, was best known for muffing a big chance, years earlier, in the last few laps.