Thames Barrier & Silvertown jetty - London - 14.10.2006

The Thames Flood Barrier has a series of gates that lie flat so ships can pass over them, but at times when there is a risk of flooding from surge tides and strong winds up the Thames, they can be swung into a vertical position.. It looks as though one has been raised - for maintenance or training purposes.
There is information at www.gov.uk/the-thames-barrier