Chapter One

It has a length of 215 miles, and is navigable for 191 miles. It is the longest river in England but not in Britain, where the Severn is longer by approximately 5 miles. Nevertheless it must be the shortest river in the world to acquire such a famous history. The Amazon and the Mississippi cover almost 4,000 miles, and the Yangtze almost 3,500 miles; but none of them has arrested the attention of the world in the manner of the Thames.

It runs along the borders of nine English counties, thus reaffirming its identity as a boundary and as a defence. It divides Wiltshire from Gloucestershire, and Oxfordshire from Berkshire; as it pursues its way it divides Surrey from Middlesex (or Greater London as it is inelegantly known) and Kent from Essex. It is also a border of Buckinghamshire. It guarded these once tribal lands in the distant past, and will preserve them into the imaginable future.

There are 134 bridges along the length of the Thames, and forty-four locks above Teddington. There are approximately twenty major tributaries still flowing into the main river, while others such as the Fleet have now disappeared under the ground. Its "basin," the area from which it derives its water from rain and other natural forces, covers an area of some 5,264 square miles. And then there are the springs, many of them in the woods or close to the streams beside the Thames. There is one in the wood below Sinodun Hills in Oxfordshire, for example, which has been described as an "everlasting spring" always fresh and always renewed.

The average flow of the river at Teddington, chosen because it marks the place wher