I went on a recce for a future walking group hike alongside the Thames in Essex. There's a disused landfill site at (appropriately named) Mucking. It has been restored and is now a splendid country park with a visitor centre at the top. It's quite view over to the new container port and worth taking your bins. The bird watchers were out in force.
Me, I meandered around on my bike (see extra- you can just see the visitor centre way over on the right ) admiring the sky and the mudflats.