With water companies reeling from criticism over sewage discharge and rising bills, Stephen Smith squelches through London's watery underworld.

'Descending into London's Victorian sewers', Stephen says, 'is like spelunking through the layers of the city's history, and reminds you that problems over water and sanitation have been the norm rather than an aberration' for centuries.

Producer: Adele Armstrong Sound: Peter Bosher Production coordinator: Gemma Ashman Editor: Richard Fenton-Smith