The incredible new £4.5bn 'super sewer' now open under London to protect River Thames

An ambitious has been initiated in London with a new £4.5 billion 'super sewer' set to slash pollution levels in one of the country's most famous waterways.

The first four sites along the Thames Tideway Tunnel have now been activated, with the full underground system set to open in 2025.

Early operational data published on Monday showed the tunnel captured close to 600,000 cubic metres of in a single day, following heavy rainfall across the capital at the end of September.

Once fully launched, the tunnel will have a storage capacity of around 600 Olympic-size swimming pools, and will divert thousands of tonnes of sewage pollution away from the .

Andy Mitchell, chief executive of Tideway, said: "We are starting to have an impact, we have got a long way to go but the cleaning up of the tidal Thames has definitely started.

"We are now on the cusp of starting to have some really tangible results. The super sewer has been switched on and is starting to protect the river from sewage pollution."

Campaign group River Action UK reported sewage was pumped into the River Thames for more than 1,900 hours in the first quarter of this year.

In August, water regulator Ofwat issued a £104 million fine to Thames Water for failing to properly manage their wastewater treatment works and networks.

Stretching from east to west London, the Thames Tideway Tunnel is 7.2 metres wide, the equivalent of three double decker buses side-by-side.

In Acton, the tunnel begins 31 metres underground, gradually descending deeper under the city and falling to 66 metres below ground level at the end of the route in Abbey Mills Pumping Station.

21 valves exist across the 15 mile system to channel sewage flows into the super sewer, though only the first four are currently in operation.

The project has taken eight years and an estimated 40 million working hours to construct, as well as billions of pounds of investment in the water infrastructure.

Once complete, the tunnel will be operated by Thames Water as part of the London wastewater network.