These photos taken deep under London’s streets reveal hidden work on the capital's 25km (15 mile)-long super-sewer.
Engineers can be seen drilling, sweeping and excavating to create the vast tunnel which will run from Acton in the west of the capital to Abbey Mills in the east.
The Thames Tideway Tunnel is expected to be completed by 2024 and aims to prevent tens of millions of tonnes of raw sewage polluting the River Thames every year.
These pictures were taken at one of the main digging sites and show workers continuing to tunnel deep beneath the surface to construct the super sewer.
Work is under way at 23 sites across the capital with four tunnel boring machines (TBM) being used to burrow deep beneath the surface, Tideway said.
The tunnel will deepen from 30m in the west to 50 or 60m deep in the east, where it will join up with the Lee Tunnel to transport all sewage for treatment.
It will be much deeper than current sewers, and mainly follow the course of the River Thames, a Tideway spokeswoman said.
Work began on the super sewer in 2016 and the project is expected to cost £3.8 billion, according to Tideway.
So far almost four miles of tunnel has been built, with four TBMs in the ground.
Around 1.6 million tonnes of rubble and debris have been removed by the river, saving 100,000 lorry trips, the company added.
Spokeswoman Hannah Shroot said that the tunnel is at a gradient so that the sewage does not need to be pumped through.
"At the moment, millions of tonnes of raw sewage pour into the Thames every year,” she said.
"The Victorian sewers are still in perfect condition but because the population of London has grown so much they are full to capacity and regularly overflow into the river.
"The tunnel we are building is the solution to that.”
