The air was damp and the temperature rose and fell by 30°, sometimes in the space of a few hours. It was also incredibly noisy – bricklayers shouting for more bricks, iron rods clanging, wooden boards thudding and hobnailed boots echoing through the tunnel. Brunel himself became very ill from over-exhaustion, and was prescribed the only treatment that would work: being bled by leeches on his forehead.
