River Thames Thames Estuary), the river is subject to tidal activity from the North Sea. Before the lock was installed, the river was tidal as far as Staines, about upstream. London, capital of Roman Britain, was established on two hills, now known as Cornhill and Ludgate Hill. These provided a firm base for a trading centre at the lowest possible point on the Thames. A river crossing was built at the site of London Bridge. London Bridge is now used as the basis for published tide tables giving the times of high tide. High tide reaches Putney about 30 minutes later than
River Thames frost fairs narrowing of the arches below the bridge, thus concentrating the water into swift-flowing torrents. In winter, large pieces of ice would lodge against these timber casings, gradually blocking the arches and acting like a dam for the river at ebb tide. The Thames had frozen over several times in the 16th century — King Henry VIII travelled from central London to Greenwich by sleigh along the river in 1536, Queen Elizabeth I took to the ice frequently during 1564, to "shoot at marks", and small boys played football on the ice. The first recorded frost fair was in 1608. The