filthiest

— Tunnels often feature in fictional journeys, so I will end with quotations from a fairly recent novel, Howard Spring's "Fame is the Spur", published in 1940, in which there is a journey from Manchester to Bradford via the Calder Valley route: "Ay, we're going through Todmorden. We'll soon be in t' tunnel, and when we get to t' other end we'll be in Yorkshire," and "Ah think this is t' filthiest tunnel in t' world."