 The Thames is maintained for navigation by powered craft from the estuary as far as Lechlade in Gloucestershire and for very small craft to Cricklade.The original towpath extends upstream from Putney Bridge as far as the connection with the now disused Thames and Severn Canal at Inglesham, one and a half miles upstream of the last boat lock near Lechlade.From Teddington Lock to the head of navigation, the navigation authority is the Environment Agency.