The Thames is one of the largest rivers in Britain. It is 250 km long and drains 10,000 square kilometres of southern England.
The Thames, (often called 'London's River') has its source as a spring in the Cotswold Hills. From here it flows east through Oxford, (where it is called the Isis) then it cuts through the chalk hills that surround the London Basin before reaching London and the North Sea.
It is tidal downstream of Teddington in west London.
