A right royal trip down the river

With all eyes now directed to the thousand boats processing down the Thames this weekend in honour of the Queen's Jubilee, the Royal Maritime Museum at Greenwich has come up with a neat exhibition: Royal River: Power, Pageantry and the Thames, curated by the ever-irrepressible Professor David Starkey.

One says "neat" because this is a very sanitised version of a very insanitary thoroughfare. For nearly 20 centuries after the Roman conquest London was the capital of the country and the river its main avenue of transport. The royals used it to get between their palaces, and the population turned out to celebrate their arrivals and their exits from the city. But, at heart, the Thames was the sweaty, rumbustious, filthy highway of a capital always growing and always bent on commerce.

The highlight of the show is the picture you see at the beginning. It is Canaletto's London: the Thames on Lord Mayor's Day, looking towards the City and St Paul's Cathedral, on loan for the first time to the UK (it comes from the Lobkowicz collection in Bohemia). It's a vision of harmony and serenity as dozens of small boats pull alongside the stately barges on a calm river. Painted between 1747 and 1755, it shows the Georgians as they wanted to see themselves, prosperous and peaceful commercial people.

The interesting thing, however, is that it is not a painting of royal or religious pageantry but of the all-too-worldly festivities surrounding the annual election of the Lord Mayor of London. Indeed it is the City of London rather than the Crown which supplies the most interesting items on display. The livery companies of London, flush with funds from the new prosperity of the late 17th and 18th centuries, flaunted their status with magnificent barges and even more magnificent pennants as the new Lord Mayor went from the City to take his oath at Westminster. Bargemasters sported huge silver disks of their livery on their arms. The rowers were all in uniform. Boats were packed with onlookers and stocked with drink to keep them well oiled. Serenity wasn't in it.

The Thames was certainly important to kings and queens. It was Henry VIII and the Tudors who recast the river from its medieval history to build fresh dockyards for the king's new navy and fresh buildings in Hampton Court and Whitehall for his pleasure. A section of the show is devoted to the efforts to give legitimacy to Ann Boleyn as Henry's second wife with a lavish procession up the Thames for her coronation. The same was done for the equally unpopular coronation of England's Catholic king, James II.

Nelson's funerary voyage was repeated, more soberly and less splendidly, by Winston Churchill. Ever conscious of historical precedents, he had determined, as a former head of the Navy, that his coffin would go by launch from the Tower to the Festival Hall. Those there at the time will not forget the sight of the dockyard cranes dipping their heads as the craft went by. But it was by then, as Churchill knew, a performance for television rather than the onlookers.

This Sunday's Jubilee procession by the Queen is less of a reassertion of tradition than a newly minted occasion for the cameras. There'll be more than 1,000 vessels stretching over 7.5 miles, including everything from Dunkirk veterans to historic barges. But there will be none of the chaos and carousing that accompanied the Lord Mayor, when small boats were allowed to bustle around at will. Security considerations won't permit it. Nor will she pass the forests of masts and the throb of trade that marked the Thames of Dickens's day. It will be a tribute to her long reign, but not to the river which once made London what it was.

Royal River: Power, Pageantry and the Thames, National Maritime Museum, London SE10 (rmg.co.uk) to 9 September