On the 11 January 1998 in Mumbai, India, the first World Laughter Day took place.
It was the idea of Dr Madan Kataria, a medical doctor who wanted to test the theory that laughter is the best medicine.
He tells Gill Kearsley how this unusual event started.
(Photo: World Laughter Day in Mumbai in 2016. Credit: Arijit Sen/Hindustan Times via Getty Images)
