Tim Zandbergen, 26, has volunteered as an aid worker at the Amsterdam Marathon for almost nine years. He began at 17 while working toward a first-aid qualification and has since helped make the course safer for runners and spectators.

He has treated heatstroke cases and had to resuscitate runners, saying that lives were saved. He carries an AED, ice, towels, a thermometer and a tourniquet in a bag on his bicycle so he can reach people quickly. His tenth edition is approaching, although he is unsure whether he will decorate his bicycle because that would be awkward.