Somewhere in London...

I drove down from Blackburn to London to drop off the hire car, with a brief pause at Manchester Airport to drop my wife Jan off so she could fly home to Sweden and work.
I was headed for the Internet Librarian International conference at Olympia in London.
Following the satnav I headed into central Londonwhere my sister lives. Somewhere just north of the river, headed towards Waterloo Bridge the traffic slowed and stopped. This highly patterned construction was on my right. I just had time to snap a photo before the traffic started up again.
I've no idea what it is, or if it is permanent or temporary. Anyone got any ideas?