It's been a long Saturday at Le Mans, and we hardly notice as we move past one-third distance at 11pm and then into Sunday. The cars are sporting illuminated numbers so we can see who's who, and leader lights tell us which racers are in contention for each class using their respective colours of red (LMP1), blue (LMP2), green (GTE Pro) and orange (GTE Am): one light for first, two for second, three for third.

In the darker corners of the circuit where you can't even make out the blacktop, dazzling headlights moving towards you flick between stability and violent side-to-side sweeps, then comes the noise - even more compelling in the sense-deprived darkness - and then the red rear lights dance away. Sneaking a peak at the drivers' view via the big screens, you get an inkling of what they're going through: a combination between night-time autobahn speeds with city-centre proximity. Some endure this intensity for more than three hours at a time.

There are lots of red eyes among the fans, none of which seem to have turned in by 1am - maybe because the campers know they'll be kept awake by firing cylinders, generators and music anyway. There's less chatter than before, but everyone at the track's edge still seems transfixed by the action. How much they are actually taking in is debatable - most have a dazed expression. Others revel in the live gig up by the Dunlop bridge, and there are plenty of places to spend your money on race-branded clobber, food and drink (some of which is well beyond the usual racetrack standards - we're in France, after all), and a fun fair to fill you with popcorn then make you bring it up again.

I've been to an Indycar race up a mountain in Japan, which was pretty unique, but tonight is my most intoxicating motor-racing experience so far, and it's this blurred border between Saturday and Sunday that defines Le Mans for me.