Temperatures reached minus 5 degrees overnight across the capital yesterday (January 12) and had barely topped zero by the time participants gathered in Chinatown that afternoon.
Hordes of bare legs then quickly headed down to the Tube in their underwear of choice, before gathering at Waterloo station.
One group of women kicked their legs with raised arms while dressed in coloured knickers.
Others were seen strutting down escalators, taking selfies on the platform or posing inside a train carriage as they showcased an array of underwear styles and colours.
From pink knickers to black Y-fronts to grey boxers adorned with red hearts, people were smiling and laughing as they took part in the free event.
Some added flair to their clothing, with one man dressed in a white shirt, black tie and brown waistcoat, while another opted for a more cosy look in an orange puffer jacket, orange beanie and blue scarf.
The Facebook event instructed participants to dress in “pants as normal or low-key as possible, so it looks like you’ve just forgotten your trousers”.
The annual event was described as “a fun activity just for the sake of fun”.
Reporting by PA.
