As we move upstream from the lively waterfront of Liverpool and Wirral, the river broadens and the whole character of the Estuary changes dramatically. Suddenly we are surrounded by wide skies, salt marshes and sandbanks. Apart from the occasional freighter heading up the channel to Garston Docks or the Manchester Ship Canal, there's little to disturb the flocks of wheeling wildfowl which have made this area internationally recognised for wildlife conservation.