The oldest bridge on the River Thames was discovered last summer in excavations at the Eton rowing lake at Dorney in south Buckinghamshire. In fact, the possible remains of two bridges were discovered, one Bronze Age, one Iron Age. The earlier consisted of two lines of timbers on opposing banks of the channel - the surviving timbers did not go right way across. There were unfortunately too few rings for tree-ring dating, but two timbers have been radiocarbon dated by the British Museum, one to 1100 ± 50 bc, the other to 1200 ± 40 bc which between them calibrate to between 1300 and 1400 BC.

Alongside were two parallel lines of timbers forming the later structure, this time running right across the channel, a distance of approximately 35 metres. Again, samples from two of the timbers were sent to the British Museum and radiocarbon dated at respectively 500 ±50 bc and 470 ± 50 bc. However, as these dates fall into the notorious radiocarbon ‘wiggle’ in the Iron Age, they can only be calibrated loosely to between 800 and 400 BC.

The River flows in from the top left, and then, half way down, cut a former channel to the right (Area 3) where the bridges were discovered.

It then rejoined the modern river bottom right.

Were these structures really bridges across the River Thames? As discovered they are merely running across a silted up channel. This could possibly be the channel of a tributary but it is more likely to be the channel containing half the river running round an island with the remainder of the Thames flowing along the course of the present river: the sediments indicate a fast-flowing channel, more likely to be half the main river.

The excavation is taking place in advance of the Eton Rowing Lake, a rowing lake to be built to international standards, one and a half miles long, which Eton College are constructing on the north bank of the Thames at Dorney, South Buckinghamshire. 80 hectares of the 150 hectare site are to be dug out, but Eton College have joined with the Oxford Archaeological Unit and are taking this opportunity to turn it into a major educational event, and it will be excavated over a number of summer seasons with the help of students and other volunteers.

The most obvious feature is the existence of a series of former channels of the River Thames. These were incised at the end of the last glaciation and after the ice retreated and the climate warmed they gradually silted up during the mesolithic.

By the Neolithic however increased flow re-activated the major channel which crossed the middle of the site. This was the prehistoric river Thames, and nearly 2 km survives within the site. Sealed within this alluvial sequence are occupation horizons of Later Mesolithic, Neolithic and Bronze Age date.

A notable feature of the excavation was that extensive use was made of volunteers. The site has a campsite with tents provided, complete with shower block. The cost is £30 a week for the first two weeks - which includes food - thereafter participation is free. The 1996 excavations are now concluded, but volunteers are being accepted for 1997. If you would like to take part, please contact Denise Price at the OAU on 01865 204642 and ask for an application form.

(The full account, together with numerous colour photos, was published in Current Archaeology 148)

Postscript. The 1996 excavations uncovered two wooden waterlogged structures, more Neolithic occupation horizons east of Site EX1, the Bronze Age Barrow cemetery to the southeast and the Middle Bronze Age inhumation cemetery and settlement. There were also further wooden bridge abutments - are they really further bridges?

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