Hundreds of people stripped off their trousers to take a half-naked trip on the London Underground.
Crowds met outside the National Gallery in Trafalgar Square on Sunday for the 10th annual No Trousers Tube Ride before heading underground where they boarded trains on different Tube lines across the capital.
More than 100 people piled on to the Piccadilly Line, where they struggled to remove their trousers due to the large crowds.
Regular Sunday passengers were left bewildered as men and women sat in their brightly-coloured underwear talking or reading, or taking pictures of each other.
After changing to the Jubilee Line at Green Park, the group got off at Canary Wharf to do some aerobics on the platform before jumping on another train.
Other groups set off for London landmarks, including one heading to Parliament.
Sisters Tessa and Matilda Deterding said they had come for the first time because they liked the idea behind it.
We read about it and thought it sounded hilarious. I wasn't nervous about it. I quite like the sentiment behind it, instead of a stiff upper lip it's having a bit of a laugh.
The London event was organised by the Stiff Upper Lip Society, which asked participants to "avoid thongs/budgie-smugglers/anything see-through though, as we aim to amuse, not offend, fellow Underground users".
One of the organisers, Farhan Rasheed, said there was not really an aim to the event, it was just a bit of fun.
There is no point to it, we are not campaigning or raising awareness of anything. People just have fun doing it, it's a bit of a nonsense day out. You very rarely get people who are offended. It's London and London is used to this stuff, they take it in their stride and get back to their book.