[1] A 2 ft 6 in (762 mm) narrow-gauge railway was laid in the tunnel and from August 1870 a cable-hauled wooden carriage conveyed passengers from one end to the other.

The opening of the toll-free Tower Bridge nearby in 1894 caused a drop in income and the tunnel closed in 1898, after being sold to the London Hydraulic Power Company.

[5] This was bored through a stable layer of the London clay that lay 22 feet (6.7 m) below the river bed, below the soft alluvial deposits that had plagued the construction by Brunel of the earlier Thames Tunnel.

The tunnel was laid with 2 ft 6 in (762 mm) gauge railway track and a single car, carrying a maximum of 12 passengers, cable-hauled by two 4-horsepower (3.0 kW) stationary steam engines, one on each side of the river.

The tunnel opened to pedestrians on 24 December 1870[9] at a toll of 1⁄2d[13][page needed] and became a popular way to cross the river, averaging 20,000 people a week (one million a year).

[15] In September 1888 the subway briefly achieved notoriety after a man with a knife was seen in the tunnel at the time when Jack the Ripper was committing murders in nearby Whitechapel.

[16] In his Dictionary of London, Charles Dickens Jr commented on the smallness of the tunnel: "there is not much head-room left, and it is not advisable for any but the very briefest of Her Majesty's lieges to attempt the passage in high-heeled boots, or with a hat to which he attaches any particular value.

"[17] The Italian writer Edmondo De Amicis (1846–1908) gave a description of a passage through the subway in his Jottings about London: As I was thinking of these things I disappeared from the world indeed, going down a lighted spiral staircase which buries itself in the earth on the right bank of the Thames, opposite the Tower.

I went down and down between two dingy walls until I found myself at the round opening of the gigantic iron tube, which seems to undulate like a great intestine in the enormous belly of the river.

When then you have reached the middle and no longer see the end in either direction, and feel the silence of a catacomb, and know not how much farther you must go, and reflect that in the water beneath, in the obscure depths of the river, is where suicides meet death, and that over your head vessels are passing, and that if a crack should open in the wall you would not even have the time to recommend your soul to God, in that moment how lovely seems the sun!

I believe I had come a good part of a mile when I reached the opposite opening on the left bank of the Thames; I went up a staircase, the mate of the other, and came out in front of the Tower of London.

c.xcvii) authorising the sale of the tunnel to the London Hydraulic Power Company (LHPC) for £3,000 (worth over £429,956 in 2023[20]), and the subway closed to pedestrian traffic in 1898.