New Tunnel Under The Thames -- Working grouting cement into the cast-iron tunnel linings in the first section of the new tunnel. Beyond them is the air lock where the tunnel is being driven further along the Thames. It will, when finished, be over 500 yards long, and 8 ft in diameter, so that a man can comfortably walk along it. A new tunnel is being constructed 30 ft beneath the Thames at Battersea to carry power cables from the power station under the river to Chelsea Embankment. It is being driven through the blue clay by exactly the same method as is used by London Transport to make a new Tube - relays of men working in compressed air. November 22, 1948. (Photo by Fox Photos).