Economic justice campaigners who have occupied an abandoned office block opened it to the public today as the "Bank of Ideas".
The Occupy London group, who have also occupied space outside St Paul's Cathedral and Finsbury Square in Islington, north London, have organised a series of events to mark the opening.
Fashion designer Dame Vivienne Westwood is also expected to speak at the Occupy London camp on the steps of St Paul's Cathedral this afternoon.
The office building, at Crown Place in Hackney, east London, belongs to, but is not occupied by, UBS and no business transactions take place there.
Occupier Spyro Van Leemnen, 27, from London, said: "It is about reclaiming space. It is symbolic for us because we know so many homes have been repossessed.
"We think it's completely unfair for the banks to have spaces like this unoccupied and abandoned.
"We occupied to give it back to the public."
He added: "This is the real big society that David Cameron has failed to achieve."
Two out of four floors have been cleaned overnight and are open to the public, Mr Van Leemnen said.
The occupation will not resemble the St Paul's Cathedral camp as visitors have been asked not to bring sleeping bags.
The group said drugs and alcohol will be banned.
A UBS spokeswoman said: "We are aware of the situation and are taking appropriate action." PA