An estimated 3,500 commuters dropped their trousers in New York to celebrate the 10th annual No Pants Subway Ride.They boarded trains at a designated time, and, once travelling, stripped their 'pants' off, leaving those not in the know open-mouthed. They reached the city's Union Square subway station around the same time - still with no pants on - and packed out the famous attraction. There were two requirements in order to be part of the flash-mob - to be 'willing to take pants off on subway' and 'able to keep a straight face about it'. Participants are not allowed to speak to each other, and, if challenged by members of the public, they have to pretend to have simply forgotten their trousers. Established by fun-seekers Improv Everywhere in 2002, the event has now spread across the globe, with tens of thousands taking part in 50 cities, from Adelaide to Zurich. In London, a more modest band of about 100 joined in the event, billed locally as the No Trousers Tube Ride to avoid confusion over the different meaning of the word 'pants' in the UK. The thrill-seekers made the journey on the Bakerloo Line from Charing Cross to Paddington and back surrounded by bemused commuters who had no idea what was happening. The Johannesburg version of the event ended up with 34 people being accused of public indecency and carted off to a police station in handcuffs, before being released without charge. "It was very funny," said Kuba Granicki, "They wanted to charge us with public indecency, but then realised there was no indecency."