Hundreds of people dressed as Father Christmas have descended without warning on Liverpool Street Station.
The flash-mob, dressed in red robes and white beards, claimed to have no agenda other than "spreading cheer".
Having arrived en masse - to the surprise of travellers - they began dispersing among the many drinking establishments in the City.
But organisers warned the many Santas against drinking irresponsibly because it was "bad for your elf".
Their manifesto read: "Anyone is welcome. The only prerequisites are that you arrive in a complete Santa outfit.
"Dazzle Japanese tourists with your flair and panache.
"Santa will begin his epic journey through the streets of London, spreading cheer and frequenting a few bars on the way."