Take a ride through London's £4bn 'super sewer' that will help clean up the River Thames

ITV News London Reporter Rags Martel cycles through London's 15 mile-long super sewer

As London's population has grown over the decades, so too has its sewage problem.

The capital's sewage system was built more than 150 years ago, and was orginally designed to cope with the waste of four million people.

Now, the creaking system can no longer handle nine million people using London's toilets.

As a result, every time there is any rain, excess waste is being dumped into the River Thames. Even a light drizzle of rain causes untreated sewage to spill into the Thames from London's Victorian sewer network. This adds up to tens of millions of tonnes every year.

But a £4 billion 'super sewer' will help protect the Thames from pollution by preventing sewage was spilling into London's iconic river.

The new 15 mile-long, 7.2 metres wide tunnel is being built to ease the pressure, intercepting, storing and transfering sewage waste away from the Thames.

ITV News London took a bike ride through the tunnel the width of three double decker buses.

Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...