Letter from Sir Marc Isambard Brunel... with engraved letterhead of the Thames Tunnel, 1842
Letter from Sir Marc Isambard Brunel to his granddaughter Sophia Hawes, 10 March 1842 with engraved letterhead of the Thames Tunnel.
Manuscript ref: NMM AGC/1/45
The Thames Tunnel links Rotherhithe on the south bank of the river and Wapping on the north. Built between 1825 and 1843, it was the first underwater tunnel in the world and is 406 metres long, 7 metres high and 11 metres wide.
The letter explains how Marc Brunel invented the tunnelling shield, which was patented in 1818 and used to create the tunnel. He got the idea from observing a piece of wood that had been attacked by woodworm. He noticed how they burrowed through the wood and that the same principle could be applied to a shield.
This consisted of 12 vertical cast-iron frames, each three feet wide (just under a metre), arranged side-by-side across the construction area. Each frame contained three cells in which the tunnellers worked. There were 36 cells in all and workers were protected from the earth in front of them by horizontal boards. Each board was moved forward as a few inches of earth was removed from behind it. Then, when a whole section of earth had been removed, the shield itself was advanced and the process was repeated.
Construction of the tunnel began in 1825 at Rotherhithe with a ceremony in which Marc Brunel laid the first brick and his son Isambard Kingdom Brunel laid the second. William Armstrong was appointed resident engineer and Isambard was his assistant until Armstrong resigned in April 1826, when he took over that leading role. Henry Maudslay’s Lambeth engineering works supplied the tunnelling shield.
The project had several difficult phases. In May 1827 the river burst through the tunnel at high tide. No one died but work on the tunnel was halted for six months while the consequences were dealt with. In January 1828 there was another flood and six people were killed. Isambard was pulled unconscious from the water and was lucky to survive. These incidents made the Thames Tunnel Company directors nervous and, while Isambard convalesced, Marc had to justify increased expenditure and clear up the site so that work could recommence. Instead, in August 1828, the directors decided to stop the project and the construction site and shield were bricked up until work resumed in 1835.
Although built as a road tunnel for horse-drawn vehicles, only foot passengers could use the tunnel when it opened in 1843. By then lack of funds meant that the construction of roadway approach ramps had to be abandoned and stairs were installed instead. In the 1860s the Tunnel was converted to carry the East London Railway. It is now part of the underground network as the East London Line and carries 14 million passengers a year under the river.
The Brunel pump house for the tunnel can still be seen at Rotherhithe and marks its position, close to the historic ‘Mayflower’ tavern and the fine Wren parish church of St Mary. It is a very small but well-preserved corner of the old Thames waterfront, easily reached by underground (Rotherhithe, or a ten-minute walk Bermondsey or Canada Water).
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