Was in the City around lunch time and popped over to the South Bank to see the completion of, well, not sure what to call it. But it was when the final block of ice was put into place for the Allan Kaprow "happening" called Fluids.
This will be left outside the Tate Modern to gradually melt (given the current cold weather, not that quickly): water changing from solid to fluid. More information can be found here.
To be honest not entirely sure what is the artistic value. Entertainment and I-was-there value maybe, but art?
Ah, the problems of modern cultural life! :)