The whole square and all the surrounding streets were served by a network of public address speakers, out of which music was pumped all day long. It was hard to make out what it was most of the time because the system was pretty ropey, and the sound just thumped and blared and echoed indecipherably around us, but as we climbed to the top of the Tiananmen Gate a few minutes later, we began to hear much more clearly what it was we were listening to.

The Tiananmen Gate, I should first explain, is a tall, flat-fronted structure with arches at the bottom through which you pass into the Forbidden City, and a large balcony across the top, behind which is a series of meeting rooms.

The Gate was built during the Ming Dynasty and used by the Emperors for making public appearances and proclamations. The Gate, like Tiananmen Square, has always been a major point of focus in the political history of China. If you climb up to the balcony you can stand on the spot from which, on 1 October 1949, Chairman Mao proclaimed the founding of the People's Republic of China. The spot is clearly marked, and there is an exhibition of photographs of the event clustered around it.

The view across the immensity of Tiananmen Square from here is extraordinary. It is like looking across a plain from the side of a mountain. In political terms the view is more astounding yet, encompassing as it does a nation that comprises almost one quarter of the population of this planet. All of the history of China is symbolically focused here, at this very point, and it is hard, as you stand there, not be transfixed by the power of it. It is hard, also, not to be profoundly moved by the vision of the peasant from Shao-Shan who seized that power in the name of the people and whom the people still revere, in spite of the atrocities of the Cultural Revolution, as the father of their nation.

And while we were standing on this spot, the spot where Mao stood when he proclaimed the founding of the People's Republic of China, the music we were having played at us by the public address system was first `Viva Espana' and then the `Theme from Hawaii Five-O'.

It was hard to avoid the feeling that somebody, somewhere, was missing the .point. I couldn't even be sure that it wasn't me.

We flew to Shanghai the next day, and began to think about the dolphins which we were slowly edging our way across China towards. We went to think about them in the bar of the Peace Hotel. This turned out not to be a good place to think because you couldn't hear yourself doing it, but we wanted to see the place anyway.

The Peace Hotel is a spectacular remnant of the days when Shanghai was one of the most glamorous and cosmopolitan ports in the world. In the thirties the hotel was known as the Cathay, and was the most sumptuous place in town. This was where people came to glitter at each other. In one of its suites Noel Coward wrote a draft of Private Lives.

Now the paint is peeling, the lobby is dark and draughty, the posters advertising the `World Famous Peace Hotel Jazz Band' are written in felt tip and sellotaped on to the panelling, but the ghost of the Cathay's former grandeur still lurks high up among the dusty chandeliers, wondering what's been going on for the last forty years.

The bar was a dark, low-ceilinged room just off the lobby. The World Famous Peace Hotel Jazz Band was out for the evening, but a deputy band was playing in their place. The promise is that this is one of the only places in the world where you will still hear the music of the thirties played as it was played, where it was played. Maybe the World Famous combo keeps the promise but their deputies did not. They banged their way through endless repetitions of `Edelweiss', `Greensleeves' and 'Auld Lang Syne' interspersed with the occasional bash at `New York, New York', 'Chicago' and 'I Left My Heart in San Francisco'.

There were two odd things about this. First of all, this wasn't just for the tourists. This was the music we heard everywhere in China, particularly the first three titles: on the radio, in shops, in taxis, in trains, on the great ferries that steam continually up and down the Yangtze. Usually it was played by Richard Clayderman. For anyone who has ever wondered who in the world buys Richard Clayderman records, it's the Chinese, and there are a billion of them.

The other odd thing was that the music was clearly completely foreign to them. Well, obviously it was foreign music, so that's not altogether surprising, but it was as if they were playing from a phrase book. Every extempore flourish the trumpeter added, every extra fill on the drums, were all crashingly and horribly wrong. I suppose that Indians must have felt this hearing George Harrison playing the sitar in the sixties, but then, after a brief indulgence, so did everybody else; clumsy replications of Indian music never supplanted the popular music of the West. When the Chinese listened avidly to mangled renditions of 'Auld Lang Syne' and `Little Brown Jug', they were obviously hearing something very different to what I was hearing and I couldn't work out what it was.

Travelling in China I began to find that it was the sounds I was hearing that confused and disoriented me most.

It occurred to me, as we tried to find a table in one of the more muffled corners of the bar, that the dolphins we had come to look for must be suffering from the same kind of problem. Their senses must be completely overwhelmed and confused.

To begin with, the baiji dolphin is half-blind.

The reason for this is that there is nothing to see in the Yangtze. The water is so muddy now that visibility is not much more than a few centimetres, and as a result the baiji's eyes have atrophied through disuse.

Curiously enough, it is often possible to tell something about the changes that have occurred during an animal's evolution from the way in which its foetus develops. It's a sort of action replay.

The baiji's eyes, feeble as they are, are placed quite high up on its head to make the most of the only light that ever reaches them, i.e. from directly above.

Most other dolphins have their eyes much lower down the sides of their heads, from where they can see all around them, and below; and this is exactly where you will find the eyes on a young baiji foetus.

As the foetus grows, however, its eyes gradually migrate up the sides of its head, and the muscles which would normally pull the eyeball downwards don't even bother to develop. You can't see anything downwards.

It may be, therefore, that the entire history of soil erosion into the Yangtze can be charted in the movement of a single baiji foetus's eyes. (It may also be that the baiji arrived into an already turbid Yangtze from somewhere else and just adapted to its new environment; we don't know. Either way, the Yangtze has become very much more muddy during the history of the baiji species, mostly because of human activity.)

As a consequence, the baiji had to use a different sense to find its way around. It relies on sound. It has incredibly acute hearing, and 'sees' by echolocation, emitting sequences of tiny clicks and listening for the echoes. It also communicates with other baijis by making whistling noises.

Since man invented the engine, the baiji's river world must have become a complete nightmare.

China has a pretty poor road system. It has railways, but they don't go everywhere, so the Yangtze (which in China is called the Chang Jiang, or 'Long River') is the country's main highway. It's crammed .with boats the whole time, and always has been - but they used to be sailing boats. Now the river is constantly churned up by the engines of rusty old tramp steamers, container ships, giant ferries, passenger liners and barges.

I said to Mark, 'It must be continuous bedlam under the water.'

'What?'

'I said, it's hard enough for us to talk in here with this band going on, but it must be continuous bedlam under the water.'