A 22-year-old man is brought into the emergency department by two workmates about ninety minutes after a scaffold pole swung loose on a building site and struck him on the left side of the head. He was not wearing a helmet, did not fall from any height, and has no other injuries. He has vomited twice in the car park, says his head is getting worse rather than better, and keeps drifting off to sleep while his friends are giving the history.