Whereas she was assured of enthusiastic, heavily policed crowds, notwithstanding a rump of well-behaved republicans, monarchs in an earlier age took to the water with trepidation. One can see why. Thousands made their living from the Thames, but none was more alarming than the river's watermen, who ferried people across the river. Spectacularly foul-mouthed, their vocabulary was known as "water-language" – presumably the forerunner of estuary English. In fact, they were so indiscriminating in whom they'd insult it's been suggested Handel's Water Music was commissioned not for its inspirational qualities, but to drown out the jeers and taunts they would have hurled at George I as he made his way along the river. As one observer commented, "Remarks which on land would have been treasonable were regarded as a joke upon the Thames."

I like the idea of a fraternity of river folk who defied even royalty. In many ways these men epitomised the spirit of the Thames which has played the part of a character, with a strong personality, in every era of British history. Without it, London wouldn't be London. Nor would Britain ever have become Great. I'd go even further and suggest that, though the Thames is a trickle in comparison with behemoths like the Nile or the Amazon, it is the most famous and most influential river in the world.

Of course, I may be biased. Not only is my mother a Londoner, but my roots probably lie among early settlers who lived by the Thames and gave their name to a village where, at the quaintly named Goring Gap, the river bursts out of the Chiltern hills and flows east towards the city.

But I suspect everyone feels the tug of the Thames. Over the centuries the river became a pivotal part of the city, not just for the jobs it offered, but as a public venue, where commoners and aristocrats played out much of their life. In winter, frost fairs were held on ice, with market stalls, skating, and bear baiting. During the Great Fire of London, it offered escape to hundreds, an event described by Samuel Pepys who, a year earlier, during an outbreak of the plague, noted with dismay how few boats were plying the Thames.

By 1700, it's estimated the river was handling 80% of the country's imports, and 69% of its exports. As London's most passionate biographer Peter Ackroyd writes, "most Londoners earned their living directly off the river or by means of the goods which were transported along it."

Yet if it were famous only for trade, the Thames would be just like any other major waterway. What sets it apart is that, with the exception of the Mississippi, I doubt if any river has been more frequently and powerfully evoked in literature and art. Turner and Whistler immortalised it in their eery depictions of a place dogged by fog and storms, but nobody has done more for the Thames's reputation than Charles Dickens.

For him it was a sinister, evil-smelling presence, a living symptom of the death and decay that defaced Victorian London. When Dickens's characters dredged it for corpses, or paced its banks contemplating suicide, the Thames entered the popular imagination as a person in its own right, and one you'd rather not bump into at night. Indeed the word tamasa, from which Thames comes, means "dark river", and many have found it unsettling. Joseph Conrad called it "one of the dark places of the earth". Despite, or because of this, it remains inspirational, and even today's novelists are drawn to it, as if any story set in London that does not mention it is guilty of neglect.

I once spent a night on the Thames, sleeping in a barge. I went to sleep horizontal, and woke up like a submarine diving for the seabed. For a frightening moment, with the barge beached on mud, it seemed as if the river had abandoned the city. I didn't feel right until the boat was once more afloat. In every sense, this mysterious stretch of water keeps the city, and Britain, on an even keel.