Cyclist had, I guess, hit the ground hard and awkwardly after a collision with a pedestrian, who was apparently unhurt. Cyclist was lying on the road screaming in pain, while the pedestrian comforted her and the Margiotta's delivery van's driver called the ambulance and acted as hi-viz barrier to oncoming traffic.
Wasn't much I could do aside from be the barrier at the other side, so I did that til the ambulance arrived.
She'd stopped screaming by this point, feet were behaving themselves and she was coherent enough to talk a friend who'd arrived through the process of calling her work, so hopefully it's nothing worse than a thumping.