The now complete tunnel runs 25km from east to west London and is around 70m at its deepest.

Tunnelling was completed earlier this month when TBM Selina broke through the shaft at Abbey Mills, ending her 5.5km journey from Chambers Wharf.

Mousa Khalifeh, Senior project manager at Chambers Wharf, described it as a major achievement.

“This project is all about protecting the Thames from sewage pollution – and with the outer shell of the tunnel now complete, we’re a step closer to bringing London the healthier river it deserves,” he said.

To celebrate the milestone a live music performance will take place 70m underground in the tunnel.

The performance, from London-based composer and musician Rob Lewis, fuses multi-instrumental music with the sounds of the sewer construction, capturing the unique acoustic properties of the space. It will be live streamed on Tideway’s YouTube channel.

The piece represents the journey and positive environmental impact of the new sewer and includes field recordings from Tideway’s construction.

Tideway chair Sir Neville Simms said completion of the tunnelling was testament to the hard work and contributions of thousands of people and organisations over many years – and brought closer the ultimate goal of a cleaner River Thames.

“This performance celebrates a significant milestone in our efforts to create a more sustainable London for our growing population and we are pleased to commemorate the end of tunnelling in such a unique way,” he said.

Environment minister Rebecca Pow described Thames Tideway as a “phenomenal feat of British engineering”.

“The tunnel will prevent millions of tonnes of sewage overflowing into the river, helping to improve water quality and allowing marine life to thrive further. Our partnership with Tideway has been an extraordinary success and I want to thank all those involved for their hard work on this incredible project, and I look forward to seeing its completion,” she said. 

The Tideway project is due to be completed in 2025, following secondary lining, connection and testing works.