I'm not sure if it's the claustrophobically low roof or the water that drips down from it that makes this such an unsetting space to pass through, but there's definitely something uneasy about the wooden bridge that passes through Tunnel 170 at Bradwell. It was closed recently for engineering works, but to me it looks exactly the same as it always has done... ancient, threatening and dark, with the river running underneath and trains thundering by overhead.