This is a vision of the dark Thames, of 'Old Father Thames' as an awful god of power akin to William Blake's Nobodaddy; and, in Blake's poem, Jerusalem, “Thames is drunk with blood”. In this film there is something fearful about the river, something monstrous, recalling Conrad's line in Heart of Darkness that “..this also has been one of the dark places of the earth.” Walking along the banks of the Thames, downriver, approaching the estuary, it is possible to feel great fear. One of the possible derivations of the word Thames itself is tamasa meaning “dark river”; the word is pre-Celtic in origin, so we have the vision of an ancient, almost primeval, time.

And yet there is beauty and sublimity in terror. Raban has learned something from the great artists of the river, such as Turner and Whistler, and portrayed the Thames as clothed in wonder.

Raban is also concerned with the river's history - liquid history, as it has often been called - but the principal impression is of the permanence of these waters. The Thames does not live in human time. It lives in geological time. The human figures in the early photographs, depicted here, are smudged and faint; they are its human votaries, already fading into invisibility. Time is therefore one of the elements of Raban's film. What is time upon the river? The Greek philosopher, Heraclitus, used the river itself as a token of flux and transience. You cannot step into the same river twice. It is always flowing and changing. But something lingers - some spirit, some atmosphere, some presence, invoked in the words of T.S. Eliot's poetry read here by the poet. There is some brooding life that persists through time.

That is why in many respects it is a visionary film. There are moments of light and colour that lift the spirit with exaltation. There are giant shapes and structure that fill the mind with awe. There are passages of mist and turbulence that recall the primaeval Thames of swamps and marshes. The multifold images of the river run through this film like the currents and tides of the water itself. It is a film, in every sense, of great fluency. The sounds, as well as the images, of the river are of great importance. There is a continual clangour, a loud lament, with the sound of machinery fighting against the lap of the water and the cry of the seagulls.

It has also been a river of trade, and a river of power. Its docks and wharves and factories were once part of the great machine of empire - the machine of oppression. That is why it is known as a dark river. It has been touched by sweat, and labour, and poverty, and tears. Yet it still calls to the forlorn and the neglected, with some siren-song of darkness. It is the great vortex of suicide. The machinery has now been dismantled. The battered industrial landscape has long since become derelict. There are signs of filth and decay everywhere, of rust and of rotten wood. The empty wharves and docks are like the relics of some abandoned civilisation, as mysterious as Maya and Inca monuments left to decay. Yet of course the river was already ancient before those civilisations began.

Raban's other films encircle around the neighbourhood of the Thames - Canary Wharf, the people upon the Isle of Dogs - as if around some whirlpool of destiny or desire. In these films the Thames becomes a vast and brooding presence. It becomes a living organism with its own laws of growth and change. We get the sense that London is not controlling it. It is controlling London. It is London.