It most certainly is an impressive sight, although i have never seen it raised. I would love it if you could post a picture, if you ever get the opportunity, showing the tidal variation. Even more impressive when you realise that, without it, a potential £80bn worth of property and infastructure would be at risk.
rdave13 In the future, if the sea level rose 6ft or so then a larger, permanent barrier would need to be put in place. I think that may be a long way off though.
I may be talking complete guff here (again) but a 'bloke dahn the pub' once told me that part of the London flood defence strategy involves potentially sacrificing low lying areas of Kent/Essex, within the Thames Estuary. Is that right?