A century and a half after the Great Stink forced politicians to think seriously about a sewer system for London, vast quantities of raw sewage are once again polluting the Thames at an alarming rate.
The government has announced plans for the Thames Tideway Tunnel, a huge sewer to solve the problem, but completion will not be until 2020 and the project will cost an estimated 2 billion pounds.
Meanwhile, experts warn of the current health risks to river users, including Olympic rowers and canoeists in 2012.
Environmentalists fear a repeat of the sewage dump in 2004 that killed thousands of fish.
A super sewer has been commissioned, officially known as the Thames Tideway Tunnel.
The deepest tunnel ever built under London, the project will cost two billion pounds and not be finished until 2020.
At 35km long, it's the deepest tunnel ever built under London and will require engineering at the limits of current technology and with the hefty price-tag will come years of riverside engineering works.
Once finished, will it really make the Thames a river fit for salmon, a fish whose numbers reflect the purity of the water, or is such a target unrealistic? Some are asking whether such an expensive sewer upgrade is really necessary.