For Those in Peril...

This is why you really need to pay attention if you go down to the Thames foreshore. 
This pair were on the foreshore at the other end of the building and didn't notice that the incoming tide had covered the beach, cutting them off from the steps. They had to climb across the slippery wooden pillars, hanging on to the chains, to get back without getting wet. 
(I was watching from Tower Bridge and would have phoned the RNLI if they looked like getting properly stuck or falling in, but they made quite steady progress back to safety.)