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Hordes of Londoners are set to strip off and board the London Underground half-naked as part of No Trousers on the Tube Day which is celebrating its tenth anniversary.

Sixty-six people have already pledged to attend the annual event on January 13, with almost 200 more interested on Facebook.

Hundreds of half-naked travellers joined the stunt last year, with many braving the cold to sport brightly coloured underwear.

The event kicks off in front of the National Gallery at 2.30pm, before those take part split into groups and take to the Tube.

Teams will then jump aboard trains and travel around town before returning to The Chandos pub in Trafalgar Square for an after-party.

Participants are asked to “avoid thongs/budgie-smugglers/anything see-through though, as we aim to amuse, not offend, fellow Underground users.”

The event is part of the worldwide No Pants Subway Ride, which began in New York in 2002 and has since spread to over 60 cities around the globe including Tokyo, Jerusalem and Moscow.

Photos from last year’s event show whole carriages of trouserless Tube riders taking part in the stunt.

Organisers The Stiff Upper Lip Society said on Facebook: "This is for the fun of it, and articles of clothing like skirts, shorts, kilts, and dresses don’t count, because people are encouraged to revel in the absence of trousers, and not replace trousers with other clothing.

"The point is to relax and enjoy the humour inherent in people not wearing trousers.

"Please don't wear anything overly close-fitting (so no thongs, banana hammocks or mankinis), nothing see-through, nor so flimsy one is falling out of it, or kilts without anything underneath.

"We don't want people to be disgusted, I personally do not wish to be arrested, and we want to stage this event for decades yet.

"The trouserless part of the event is all underground, and it is warm down there.

"The only chance you'll have to be cold is when we meet up at Trafalgar Square at the beginning, any surfacings Troop Leaders select, and when we walk to the pub at the end."