The £4.2 billion Thames Tideway Tunnel, will run for 15 miles below the capital, and is currently the largest infrastructure project to be undertaken by the UK water industry.

Bazalgette Tunnel Limited, made up of a consortium of investors, has been awarded its licence as a new regulated utilities business – separate from Thames Water – by water and sewage regulator OFWAT.

The huge project, which along with the already-constructed Lee Tunnel will help stop 39 million tonnes of untreated sewage getting into the Thames each year, was given planning approval last year.

Construction work is expected to take seven years to complete.

Bazalgette Tunnel Limited takes its name from Sir Joseph Bazalgette, the 19th-century engineer who built a system of interceptor sewers, which are still used to keep sewage out of the Thames but do not have the capacity to cope with the capital’s growing population.