This is a lovely film about the Thames well worth a watch
https://player.bfi.org.uk/free/film/watch-colour-on-the-thames-1935-online
Article in the Guardian about the Lea
www.theguardian.com/artanddesign/2017/apr/05/the-river-london-forgot-lea-valley-reborn-leaway-path
Below a couple of views of the Thames in 2020 in stark contrast to the 1935 film above.