A gigantic tunnel deep under London partly built with Chinese money and passing near the Houses of Parliament and the MI6 intelligence agency’s headquarters sounds like the scenario for a James Bond film.

Yet the ￡4.1bn Thames super-sewer, which aims to end the discharge of huge amounts of raw sewage and rainwater into the capital’s river, is one of the most ambitious infrastructure schemes being planned in Britain at the moment.

The complex procurement process for the 16-mile “Tideway” scheme is still in the early stages but discussions are under way to drum up sources of capital for the company that has been set up to deliver the project, and which will be at arm’s length from the UK government, the regulator Ofwat, and Thames Water – London’s water supplier.