Tony reveals how the Thames plays a vital role in keeping London - and beyond - on the move, and how it is a 24/7 operation - when the transport network is so busy during the day, it's only at night that crucial maintenance and repairs can be done. His first night shift is with the engineers and cleaners at Thames Clippers - responsible for turning around a whole fleet of commuter boats overnight, ready for the next morning.

The presenter is on the West London stretch of the Thames, and here he discovers how night-shift workers contend with the river's tides. Tony joins the fire service based at Lambeth, who deal with emergencies on the river, as they practice rescuing a body from the freezing waters in the pitch black.