Tidal waters reach Teddington, 62 miles / 100 km from its mouth, where the first lock from the sea (except for the tidal lock at Richmond) is located.
There are in all 47 locks, St John's Lock, Lechlade, being nearest the source. They face the South Downs across the Weald of Kent and Sussex and are much used for sheep pasture.
One of the Fat Badgers has travelled the whole of the British Mainland Coastline - But that was in a car.
There are thirteen long distance routes in England & Wales which have been designated by the Countryside Agency as 'Official' National Trails .
National Trails are marked with arrows and an acorn symbol or a thistle in Scotland.Ten of these are fully developed and three are still under development in places.The first National trail was the 412 km Pennine Way, opened in 1965.The central part of the route between Thetford in Norfolk to Ivinghoe Beacon in Buckinghamshire covers to the Nore, where it flows into the North Sea.At Gravesend, the head of the estuary, the Thames has a width of 0.6 miles / 1 km gradually increasing to 10 miles / 16 km at the Nore.