It is 58 million years old and 346km long. It has 80 islands, 45 locks and more than 200 rowing clubs. It’s crossed by 104 bridges and is home to 100 species of fish; briefly, in January 2006, one lost bottle-nosed whale joined the throng.
But the River Thames, the second-longest in Great Britain, is more than a bunch of statistics. It’s the lifeblood of southern England.
It has witnessed the birth of democracy and the extravagant architectural ambitions of many a royal. And it spawned London – one of the greatest capitals in the world.
The Thames springs to low-key life in the Cotswolds. Thames Head is usually dry (though a stone tablet marks the spot), but walk a few kilometres and you might see the first waters rise at Lyd Well.
The infant Thames then flows through peaceful Cricklade; in Lechlade (home to the statue of Old Father Thames himself) the river starts to swell to around 18m across – this is its navigable limit, so it is the place to hire barges for a full Thames cruise.
From here the river squiggles towards Oxford (where it’s known as the Isis). The university city’s 'dreaming spires' are a short detour from the banks; Port Meadow, by the river’s edge, inspired Lewis Carroll’s Alice adventures and is a haven for birds.
Picking up pace
Passing George Orwell’s grave (near Abingdon) and the Iron Age hill fort at Wittenham Clumps, the river – much wider now – races through Goring and Streatley in Oxfordshire. Just after Pangbourne (one-time home of Wind in the Willows author Kenneth Grahame) you can nip to Mapledurham Estate, a handsome Elizabethan manor and watermill.
After retail therapy in modern Reading, follow the Thames to Sonning, where the charming old mill is now a dinner theatre, and on to Henley. Home of the great annual Regatta (June) and the River & Rowing Museum, Henley is the place to drink Pimm’s and stroll along the river to the pretty hamlet of Hambledon.
Food and finery
Admire historic Marlow but save your appetite (and wallet) for Bray. This is the river’s culinary capital, home to Heston Blumenthal’s Fat Duck, one of the best restaurants in the world.
The turrets of Windsor Castle lord over the now suitably regal Thames; if the Royal Standard flag is flying the Queen is home. Watch the Changing the Guard (11am on alternate days) then stroll across the bridge to academic Eton.
The Magna Carta, the original charter of civil rights, was signed in 1215 at Runnymede (visit the memorial, as well as a tribute to JFK). Further downriver, Henry VIII’s great palace at Hampton Court dominates – tour the state apartments and get lost in the maze.
Teddington Lock marks the start of the 'London River'; the waterway, now tidal, is about 100m wide here. At refined Richmond pop into 17th-century Ham House, then Richmond Park, hunting ground of Henry VIII who, thankfully, didn’t finish off all the deer – hundreds still roam.
Barnes Wetland Centre is home to more wildlife, including bats and rare birds; the Thames here is wildest – with cheering students – when the Oxford and Cambridge Boat Race glides past in April.
Central London now beckons. The river dips under Chelsea Bridge, past Battersea Park’s Japanese pagoda and the Houses of Parliament. Board a Thames Clipper ferry at the iconic London Eye ferris wheel to sail alongside the South Bank, Tower Bridge and the Tower of London, and the skyscrapers of Canary Wharf. Disembark at Greenwich for the National Maritime Museum.
From here the Thames makes its final dash past the shimmering floodgates of the Thames Barrier to the North Sea. From an initial insubstantial trickle it has grown to a world-class waterway, and as it spreads to 29km wide between Whitstable and Foulness Point, the Thames is heavy, not only with water, but millennia of history.
So you've made it to London. Here's what to do with 24 hours in the city.
This article was updated in November 2012.