The River Thames is 215 miles (346 km) long, the longest river entirely in England. (The River Severn holds the record as longest river in the United Kingdom at 220 miles (354 km) but its source is in Wales.) It rises in Gloucestershire and flows into the North Sea at the Thames Estuary via London and is navigable over the majority of its length. From the furthest navigable point upstream to the estuary, the river falls 234 feet (71 metres) so, to assist navigation, there are 45 locks along its length. This is Sonning Lock, one of three locks between my home town of Reading and Henley, famous for its Regatta. The earlist mention of a lock in this area, which was most likely a flash lock, is in 1580. The first pound lock on this site was installed in 1773. Originally built with Fir wood, this decayed very quickly and was replaced by Oak in 1787. The lock underwent a rebuild in 1868 and again in 1905 with wooden gates finally being replaced with steel gates during the winter of 2004-5. ------------------------------------------ Original Photograph 23 Jun 2013