As the poet John Burns observed, the River Thames is “liquid history”. For centuries, water gathered in the Cotswold Hills has flowed east, witnessing the rise of Oxford, Windsor, Eton and Kingston, as well as the nation’s capital city, on its meandering journey. Though it may be small on the scale of the world’s great rivers, it has been party to some momentous events in Britain’s past.

More than two thousand years ago, its turgid, muddy waters carried the invading Romans who founded Londinium; 300 years ago, it swirled beneath the hanging body of the pirate Captain Kidd; and four years ago it reflected jubilant party-goers celebrating the new millennium. For thousands of years, the river has bubbled and eddied its way through 346 kilometres of southern England before offloading its burden of sediment and secrets into the North Sea.

The earliest history of the Thames dates back millions of years to the Jurassic period, when much of southern England was covered by sea. Marine organisms accumulating on the seabed gave rise to limestone, which was later squeezed by movements in the Earth’s crust into undulating downlands.

At that time, Britain was part of a vast North Atlantic landmass, but 15 million years ago Greenland and North America split away, leaving our fledgling land jutting out of continental Europe. Without the North Sea to curtail its journey, the early Thames was a tributary of the Rhine, but towards the end of the Ice Age, melting glaciers prompted sea levels to rise. Eventually, around 10 thousand years ago, water surged over the land between Britain and Denmark (now a sandbank in the North Sea known as Dogger Bank), and inundated the area between Europe and the east coast of England, creating the Straits of Dover and making Britain an island. The Thames then became a river in its own right.

Today, Ordnance Survey acknowledges the official source of the Thames to be in a remote Gloucestershire meadow at Trewsbury Mead, although some claim the true source is 17km farther north at Seven Springs. The stream issuing at Seven Springs is called the Churn, while that flowing from Trewsbury has been called the Thames throughout recorded history. From here, the widening river flows through rolling countryside and villages, winding past Oxford, Abingdon and Wallingford and then Goring, Pangbourne, Henley and Marlow, before passing Windsor Castle and Hampton Court.

Though the river generally flows east, it changes direction at various points along its course. Close to Abingdon it flows west; from Cookham to Bray it turns south, and at Marlow and Kingston it travels north. Where it flows through Oxford it is called the Isis, which derives from its Latin name Thames is.

This name dates back to Celtic times and was adopted by the invading Romans, who harnessed the free energy source of the river’s tidal flow to carry them inland when they arrived on British shores in 55bc. They defeated resistance from local inhabitants and, at the point where the effect of the tide ceased (in those days close to the modern-day London Bridge) they built what is thought to be the first bridge across the river, thus establishing the port of Londinium.

Their choice of location was wise; by the 12th century London had become the largest and wealthiest city in England, prompting William Fitzstephen, to write in his 1173 account, A Description of London: “It pours out its fame more widely, sends to farther lands its wealth and trade, lifts its head higher than the rest.”

By the beginning of the 18th century, it was the largest city in Europe and the Port of London was the central trading post for the growing British Empire. The river was so busy at this time that Daniel Defoe estimated there were about “2,000 sail of all sorts not reckoning barges, lighters or pleasure boats or yachts” using the wharves and quays.

From 1450 to 1850 the “little ice age” inflicted bitterly cold winters on the northern hemisphere, prompting the Thames to freeze. This temporarily crippled maritime trade, but from the early 17th century provided a novel form of entertainment for Londoners in the form of “frost fairs”.

Entrepreneurs set up merry-go-rounds, organised skittle and hockey matches and roasted sheep or oxen on the river’s glistening surface. So many people were eager to buy souvenirs of the fairs that traders inflated their prices. One popular rhyme stated: “What you can buy for threepence on the shore, will cost your fourpence on the Thames, or more.”

The frost fair of 1813-14 was the last. The little ice age was coming to an end, and London’s climate was warming up. A new bridge built between 1825 and 1835 to replace the old London Bridge had much wider arches, and this improved the flow of the river. The Thames never froze again.

With the river no longer gripped by prolonged periods of freezing, the Victorians developed its potential as a transportation route. They installed locks along its length to aid navigation, so that by the end of the 18th century much of its flow was under their control.

Imported goods such as tea, coffee, ginger and cardamom, were carried from the Port of London by horse-drawn cart or barge, then transferred to canals for the onward journey inland. In return, London gained building materials and staple foods for its growing population: Buscot, on the banks of the Thames near Oxford, sent 30,000 cheeses per year to London by barge. Only when the expanding railways began to offer a faster and more efficient method to transport goods did the river trade dwindle. Its demise freed up the waterway for a new era - that of leisure boating.

From the middle of the 19th century, towns such as Maidenhead and Pangbourne flourished as people came to hire skiffs and punts for the day.

Later, boatyards added metal hoops and canvas covers to their boats, so people could sleep on board and make longer journeys.

In 1889, Jerome K Jerome published Three Men in a Boat, about his trip up the Thames with companions Harris, George and Montmorency the dog. “I often thought I could stay a month without having sufficient time to drink in all the beauty of the scene,” he gushed of the village of Hurley.

The American anglophile Henry James found the new pastime somewhat bemusing: “I know of no other classic stream that is splashed about for the mere fun of it. There is something droll and almost touching in the way that on the smallest pretext of a holiday or fine weather, the mighty population takes to boats.”

Several annual boating galas held on the river today are rooted in history.

The oldest, Doggett’s Coat and Badge race, first took place in 1715 when the Irish comic actor Thomas Doggett proposed a rowing race between newly qualified watermen operating ferries on the river. The contest celebrated the anniversary of the accession of George I and was rowed over a course of “four miles and five furlongs” (7.5km) from London Bridge to Chelsea. The race has been held every summer since then, and is thought to be the oldest annual sporting event in the world with a continuous record.

A century or so later, the Oxford and Cambridge Boat Race and Henley Royal Regatta also began drawing the crowds. Charles Dickens found the latter a little too well attended, as he describes in the 1890 edition of the Dictionary of the Thames: “The river is so inconveniently crowded with steam launches, houseboats, skiffs, gigs, punts, dinghies, canoes and every other conceivable and inconceivable variety of crafts, that the racing boats have sometimes great difficulty in threading a way through the crowd.”

Many writers, artists and poets have left us with glimpses of the river’s past character. In 1790, Wordsworth composed a poem from Richmond Bridge, called “Lines written near Richmond, upon the Thames at Evening”, while in 1819 Joseph Turner painted a panorama of the Thames titled “Richmond Hill, on the Prince Regent’s Birthday”, and Lewis Carroll penned Alice in Wonderland after picnicking on the river at Godstow with his young friend Alice Liddell. Jerome K Jerome found Maidenhead “too snobby to be pleasant” and “the haunt of the river swell and his overdressed female companion”, when he floated past the riverside town. But local historian Thomas Faulkner had nothing but praise for the stretch of river between Hammersmith and Kew. “From Kew Bridge the river flows majestically on in sweeping courses between shores skirted with villages and fine seats, passing Mortlake, Barnes, Chiswick and Hammersmith, where it is enlivened and embellished with one of the most magnificent works of art that modern skill and ingenuity have produced - the suspension bridge,” he enthused.

Feats of engineering have certainly made the modern-day Thames a different beast from the river the Romans encountered. Today, there are 45 locks controlling its flow, more than 100 bridges spanning it and 30 or so tunnels passing beneath it. Because England is tilting into the sea, the point at which the river becomes tidal has progressed inland over time.

However, with the construction of Teddington Lock in 1811, that point is now fixed. Today, the tide flows up to Teddington, and a half-tide lock at Richmond prevents too strong a current and keeps the river level. “In its natural state the river would have been much wider and slower and it would have meandered widely across its flood plain,” explains Jon Cotton, curator of prehistory at the Museum of London in the Docklands. “It probably would have been a series of braided channels. Today’s river is pretty much the product of engineering. It’s a tidal canal, totally constrained within flood defences.”

The greatest defence of all, the Thames Barrier, was officially opened in 1984 to protect London from flooding, for example during surge tides. The Barrier consists of a string of huge stainless-steel shells spanning the 520-metre-wide Woolwich Reach, concealing hydraulic power packs that can lower gates to stem the water flow when required.

Although regular high tides can be predicted well in advance, certain weather conditions can cause surge tides, which can’t be predicted more than 24 hours in advance. It is these the Barrier is designed to withstand.

When raised, the four main gates stand as high as five-storey buildings and weigh 3,700 tonnes each. Since its completion in 1982, the Barrier has been raised 88 times.

Travel by boat from Westminster to the Barrier and you get a glimpse of the ever-changing character of the river and its surrounds. The imposing Tower of London today welcomes tourists, not prisoners; once bustling docks now house sleek up-market apartments; and the Cutty Sark clipper, which raced the high seas to bring tea from the colonies, now stands in dry dock.

Close to the Barrier, in the newly named Thames Gateway, the evolution continues as developers prepare to build thousands of new properties to house London’s growing population. Reaching this transitional hinterland is a signal to the turbulent Thames that it will soon reach the North Sea and the end of its meandering journey. As it does so, rainwater trickling through the Cotswold Hills 346km away will begin travelling east to take its place, ensuring the flow of liquid history continues for centuries to come.

EXPLORE THE STORY OF THE RIVER THAMES

* HMS Belfast

Morgan’s Lane, Tooley Street

Moored permanently on the Thames in the Pool of London, HMS Belfast is a reminder of the nature of 20th century warfare.

http:hmsbelfast.iwm.org.uk

* National Maritime Museum

Park Row, Greenwich

The world’s largest maritime museum covers every aspect of ships and seafaring from prehistory to today.

www.nmm.ac.uk

* London Canal Museum

1213 New Wharf Road, King’s Cross

See how goods were transported from the Port of London across the country via the canal network.

www.canalmuseum.org.ukwhatson

* Kew Bridge Steam Museum

Green Dragon Lane, Brentford, Middlesex

The museum houses a collection of steam pumping engines and is developing a display on the history of water supply.

www.kbsm.org

* Tower Bridge Exhibition

This famous landmark contains an award-winning exhibition featuring the history and construction of Tower Bridge.

www.towerbridge.org.ukTowerBridgeEnglish

* Museum in Docklands

No 1 Warehouse, Hertsmere Road, West India Quay

Explores the 2,000-year story of river and port from Roman settlement to the regeneration of Docklands.

www.museumindocklands.org.uk

* Bramah Museum of Tea and Coffee

40 Southwark Street

The museum tells the story of how tea and coffee were sourced in the colonies and shipped to London.

www.bramahmuseum.co.uk

* Thames Barrier Information Centre

1 Unity Way, Woolwich

An exhibition explains the natural forces that prompted the Barrier to be built, shows how pollution is tackled, and profiles the river’s returning wildlife.

www.riverthames.co.ukthingstodo1231.htm

* Dolphin Sailing Barge Museum Trust

Crown Quay Lane, Sittingbourne, Kent

Explores the history of Thames sailing barges and includes the original Burley’s Barge Yard, with its sail loft, shipwright’s shop, forge, basin and barge blocks.

www.riverthames.co.ukthingstodo1199.htm

* The Riverside Museum Blake’s Lock, River Kennet, Reading

The screen house and the turbine house explore the story of Reading’s two rivers, the Thames and the Kennet. Displays include a medieval mill wheel and preserved turbine machinery.

www.readingmuseum.org.ukgalleriesblakes.htm

* The Pumphouse Educational Museum

Lavender Road, Rotherhithe

The museum houses the Rotherhithe Heritage Museum and the Lavender Pond and Nature Park. The building was built in 1929 to regulate water levels in the dock system; the Heritage Museum opened in 1991.

www.se16.btinternet.co.ukpumphouse.htm

* River Rowing Museum

Mill Meadows, Henley on Thames

The museum has won awards for its architecture. It features galleries devoted to the Royal River Thames, the international sport of rowing, and the town of Henley.

www.rrm.co.uk

THAMES RESOURCES

* The Thames Explorer Trust organises river visits for schools, community groups and adults to investigate the Thames: www.thames-explorer. org.uk

* Thames21 aims to work with communities to create clean, safe, and sustainable waterside environments: www.thames21.org.uk

* The Thames Education Network links organisations that are involved in providing education about the Thames: www.thamesweb.comaction_group.php?group_id=17

Thames Water Database of Educational Resources: www.waterinschools.comezshoppersearch_link.html

Books

* River Thames: In the Footsteps of the Famous By Paul Goldsack Bradt Travel Guides pound;10.95

* The Thames from Source to Sea - A Photographic Atlas www.getmapping.com and HarperCollins, pound;25 + VAT

* The River Thames in Verse - An Illustrated Anthology of New Poems Edited by Val Mason River Thames Society pound;9.99

* The Thames By Paul Atterbury and Anthony Haines Orion Publishing Group Pounds 9.99