If you didn't watch the old 1992 Top Gear clip above, let me explain what vintage trials are. Basically, a bunch of weedy old englishmen gather on the side of a very slippery, muddy hill and try to drive up it. The cars that they bring are true vintage sports cars, with what we would now call very low power and very high stance. Think of them like baja versions of a Caterham, only really old.
The best part about trials (other than seeing classic Bugattis tearing sideways at maybe half a mile an hour) is how involved the driver and passenger are together, as a team. The passenger is constantly bouncing up and down to give the car a little bit of extra traction. Sometimes the passenger is fully out of the car, helping to push up some mud-splattered embankment.
It's like the most cultured version of Jeep meetups, or the most brutish version of vintage sports car racing. And I absolutely love it.
(Hat tip to D and Svend!)