“Tributaries A river on a map is a simple thing. Our river starts at Trewsbury Mead, and follows a course of some two hundred and thirty-six miles to reach the sea at Shoeburyness. But anyone who takes the trouble to follow its route, whether by boat or on foot, cannot help being aware that, furlong by furlong, singleness of direction is not its most obvious feature. En route the river does not seem particularly intent on reaching its destination. Instead it winds its way”