The River Thames has been there since pre-historic times so nobody knows.
That would be the River Thames.
River Thames
The River Thames is the major river through London, cutting right through the middle of the city. There are many other rivers in London, such as the River Lee (or Lea) and the River Brent.
The river Thames (pronounced temz)
London is situated on the River Thames (pronounced 'temz'.
Thames River
The River Thames begins at Thames Head in the Cotswolds, Gloucestershire, England. It flows approximately 215 miles (346 kilometers) southeast through various towns and cities, including Oxford and London. The river ultimately empties into the North Sea at the Thames Estuary near Southend-on-Sea.
The Thames flows through London.
The River Thames has multiple confluences. One such is the confluence of the River Thames and the River Darent at Dartford.
In the 1970's, I forget what year, the Thames dried up to a trickle in July.
The river Thames.
The river Thames is in England.