LONDON, United Kingdom (AFP) — William Skannerup glanced left and right at his fellow commuters on the London Underground train network, before they nodded in agreement and pulled down their trousers to reveal colorful underwear.

Around 100 people gathered in central London on Sunday for the No Trousers on Tube Ride, a ballsy annual tradition in which people take their trousers off on the city’s busy metro system “just for fun.”

Skannerup said he was taking part after going through a “terrible breakup” and wanting to “do something different.”

“My game plan? To look as cute as possible and get a picture to use on my dating profile,” the 32-year-old told Agence France-Presse as he entered the busy train, known as the Tube.

Once inside the train, Skannerup and his fellow participants — bundled up in coats, hats and gloves on the freezing winter day — dropped down their trousers.

Commuters blushed, laughed and shielded their children’s eyes at the barefaced spectacle. “Nothing to see here,” one man told his son.

Inspired by an event which launched in New York in 2002, the challenge has become an annual ritual in London since 2009, said organizer Dave Selkirk.

“In New York, it’s called ‘No Pants,’ but that means something different in London,” where pants refers to underwear, explained Selkirk.

The brief? Participants are told to keep their underwear on and are encouraged to wear “low-key” lingerie so that “it looks like you’ve just forgotten your trousers.”

“The world is a rough place at the moment, and it’s lovely to have something that is just for the sake of fun,” said Selkirk.

Mexican couple Daniela Garcia and Fran Ruiloba joined in for the bottomless revelry after hearing about the event last year.

“I love it, it’s so cheeky, it’s so English,” Garcia said.

“It’s not illegal but like pushing the envelope a little bit, I like it,” added the 28-year-old lawyer.

“I feel silly,” giggled Ruiloba, a 34-year-old doctor. “Right now we’re just happy to take our pants off and see where that takes us.”

“It’s one of the best public transports in the world. So, if I’m going to be without trousers, I think London’s the best place for it,” Garcia added.

Will, a 28-year-old working in marketing said he might get cold feet when the time comes to bare (almost) all.

“You’ve got to try all the unique things in London... I think it’s important to do stuff that’s pushing the line a little bit,” he said.

Did he do anything to prepare for the big day? “I did some squats before,” Will revealed. “To look good.”