How would the 'super sewer' be built?

Planning officials have started looking into proposals to build a so-called "super sewer" under London.

The Thames Tideway Tunnel would create one of the world's largest sewerage networks and is designed to prevent discharges of effluent into the river Thames.

But there is strong opposition to the scheme, which would cost over £4bn and take a decade to build. Tom Bateman reports.