Hundreds of half-naked Londoners left Tube passengers stunned when they left their trousers at home to mark the worldwide No Trousers on the Tube Day.

The annual event is now celebrated in more than 60 countries around the world.

Bemused Tube passengers looked on in shock yesterday as crowds of semi-dressed men and women boarded Tube trains around the capital.

The chilly event began in 2002 in the US, when seven men threw off their trousers and rode the New York subway for a prank.

In 2016, 300 Londoners took part in the event and this year's day marks the eighth annual No Trousers Tube Ride.

On Sunday hoards of people were spotted in stations across London embracing the phenomenon – although many made sure they were off the London Underground by 6pm because of the planned Tube strike.

The Central Line responded to passengers’ queries on Twitter after one woman said she spotted lots of men “randomly wearing underpants and no trousers”.

The spokesperson for the Central Line’s twitter account said it was not a Transport for London endorsed event.

Organisers of the special day on the Tube said there are only two requirements: "1) Willing to take trousers off on the Tube. 2) Able to keep a straight face about it."