It is simply a 2–up pursuit done as a Madison.
The distance is over 6 laps at Herne Hill. And it’s based on fastest times. So no sprint laps.
Heats start with 4 pairs of riders at 4 stations. Each station has a timer. (Who brings times back to recorder please note!)
The fastest 1 or 2 pairs through to finals. More teams more heats.
First rider has a standing start. Second rider is somewhere ahead ready to be hand slung into race. First rider who is in the race comes behind second rider and slings them in.
The exchange must happen below the stayers line (blue line) As soon as it is safe and practicable resting rider must get above the stayers line.
You cannot ride through an exchange – you must go above it.