Londoners have braved freezing temperatures to take part in the annual No Trousers Tube Ride.
Trouserless travellers were spotted across the Tube network as the mercury dropped below zero on Sunday morning.
Passengers were left startled as they were met by boxers and knickers at major stations such as South Kensington and Westminster. Temperatures crept up to just 2C when the ride took place on Sunday afternoon.
Elsewhere, seminude commuters filled carriages on the Piccadilly Line and Circle Line, leaving some bystanders blushing during the brazen stunt.
People pose during the “No Trousers Tube Ride” in London (REUTERS)
This year organisers asked No Trousers riders to “keep the (under)pants as normal or low-key as possible, so it looks like you’ve just forgotten your trousers”.
Participants are encouraged to act completely normal – by reading a paper or listening to music – while being trouserless.
The No Trousers Tube Ride began in 2009 and was inspired by the No Pants Subway Ride, which was created by Improv Everywhere in New York in 2002.
It is just for fun and not a political statement or attached to a charity.
The first-ever event in New York City involved seven trouserless men boarding the subway train, one at each stop for seven consecutive stops, pretending not to notice each other.
People on the Piccadilly line take part in the annual No Trousers Tube Ride (Aaron Chown/PA Wire)
The train was stopped and eight people were handcuffed and taken into custody for not wearing trousers but the charges were later dismissed.
The following year, hundreds of people took part and, in 2008, the event went international, with nine cities participating.
Since 2010, thousands of New Yorkers have taken part in the annual prank. More than 60 cities around the world now stage the event, including Berlin, Lisbon, Tokyo and Toronto.