Tony begins his journey at the source of the Thames in Gloucestershire. He meets a professional crayfish catcher, investigates the cleanliness of the water and discovers the uses the Home Guard put the river to in WWII.

Through the beautiful Thames valley, Tony ends up at Hampton Court Palace before trying out a Victorian skiff and exploring the river's most advanced sewage plant.

Reaching central London, Tony Robinson boards an industrial working ship, explores the Physic Gardens, and gets a bird's-eye view of the river from the Shard.

On patrol with the Metropolitan Police Marine Unit, Tony gets an emergency call-out to an unexploded bomb. At Billingsgate Fish Market, he relives his teenage years working the docks.

In the second episode, Tony explores the river's role as a vital trade artery connecting the country to the outside world, going behind the scenes at London Gateway, the newest and largest container port on the Thames. Later, he visits Whitstable, famous for its oysters that come from the Thames estuary.

Tony goes behind the scenes at the iconic Cutty Sark in Greenwich, meeting with the passionate team who care for this historical tourist attraction. Later, Tony visits a metal recycling yard on the banks of the river, before heading out of London to the Hoo peninsula in Kent, where he discovers a rich history of military defence in one small fort.

Tony watches a tunneling machine being transported up the river into central London, and discovers plans to build a new tunnel under the Thames to take pressure off the crossing at Dartford. He also makes a late-night visit to New Covent Garden Market, and meets a Paralympian in training at Marlow Rowing Club.

The actor and presenter starts his journey heading up the estuary to Southend Pier, where as a young man he'd drive to with friends. But the pier was original conceived in Victorian times to attract day-trippers from London - and tempt them away from nearby Margate. It's now the longest pleasure pier in the world and, as Tony discovers when he lends a hand replacing a girder, it requires a lot of maintenance.

The actor and presenter starts the latest leg of his journey in Beckton. There he discovers how a new super-sewer is being built to help stop overflow from London's existing system ending up in the Thames. After a hair-rising cage ride down into the tunnel, Tony Robinson meets the engineer in charge of the project who explains how it will work.

The actor and presenter starts his journey in Richmond upon Thames, at Hampton Court Palace. This 1,000-room residence was King Henry VIII's favourite. Tony begins his tour by the Thames right where the loos would have been. It's also where the royals would have arrived by barge, and where merchants from as far away as Venice would have sold their fancy fabrics.

London City Airport, right in the middle of the capital, is built on an island in the Thames itself, creating unique hurdles for the people who work there. Tony Robinson finds out more about those challenges as he meets a pilot, joins the airfield operations team, and takes part in a drill with the airport's firefighters.