Today marks 50 years since the Victoria line was extended from Victoria to Brixton – opening, minus one of the stations – on 23rd July 1971.
Although the Victoria line was approved for construction in August 1962, the extension south of Victoria, which nearly went to Fulham, was only approved to go to Brixton in March 1966. Brixton was chosen to match the thinking of the time as it was expected to have a motorway built there, and a rail link would offer a park-and-ride option for motorists.
It was approved for stations at Vauxhall, Stockwell and Brixton. You might notice a missing station, Pimlico. That only approved later, in 1968, and opened a year after the railway in September 1972.
The reason Pimlico was added later is that the business case for the station was marginal, but lobbying by Westminster Council and a decision by the Crown Estate Commissioners to lend land for the station construction site to London Underground for free helped to sway the case.
In the end, the station cost £1.4 million to build, which was less than the expected fares revenue but was justified by the wider benefits to the area. This was still a time when transport upgrades had to be funded by their own income, and the wider society benefits were not included. Today it’s almost impossible to fund a railway based on revenue alone, and economic uplift around the area is a key component of the funding agreements.
The timing of the extension was fortunate, coming at the time that the initial stretch of line was opening in 1968, as that meant that many of the miners who worked on the original section were still available to work on the extension. Around 30 miners still working on the original line were boosted to over 200 miners to work on the extension.
One of the quirks of the extension being added later can be found at Victoria station. As that had been expected to be the terminus of the line when built, it had two tunnels extending southwards beyond the platforms, to provide reversing space and to store a couple of trains overnight. Those tunnels are still there, although now hardly ever used, they can be used to reverse trains if for some reason the line southwards was closed.
The first sections of the extension tunnel were dug from Bessborough Gardens north towards Victoria and south towards the river, and then under it to Stockwell. The second set of tunnels were dug separately linking Stockwell to Brixton.
One big change from the original Victoria line tunnels is that those used a new form of Tunnel Boring Machines (TBM), but the extension reverted back to being dug largely by hand using an old Greathead Shield design as the extension was too short for TBMs to be considered viable.
The northern side of the Thames and under the river was dug through nice London clay, but gravel at Vauxhall and Stockwell caused a lot of problems for the miners working in the tunnels. Stockwell was also particularly difficult as the Victoria line extension tunnels would pass within 6-feet of the Northern line tunnels.
Although most of the new tunnels were lined with concrete rings as had been pioneered for the first time on the rest of the Victoria line, they fell back to cast-iron rings under the river and where the soil was poor.
Although most of the Victoria line trains were stabled at a new depot at the northern end of the line, at Northumberland Park, they extended the tunnels beyond Brixton by the length of an additional train, so that two trains could be stored there overnight. Contrary to the occasional rumour that crops up, the tunnels didn’t go any further and were not designed to lead in any particular direction for another extension — they were purely added to store trains.
Away from the tunnelling, often the most complicated part of a new underground railway is the construction of the stations, especially if they are junctions with existing lines.
Vauxhall was the worst station to work on, for not only was the gravel layers difficult to work in, but they also had to build a large cofferdam around the station to stop the Thames from breaching through the gravels. They also used a technique that had been used earlier at Tottenham Hale to deal with very soggy grounds. They froze the ground.
Pipes were driven into the ground and super-cold fluid was pumped through the pipe network to freeze the soil and then the miners were able to dig through the frozen gravel layers to excavate the ticket hall and later the escalator shafts. A similar method was also used at Pimlico.
By the end of 1970, the tunnels were largely complete, and they were finishing off the stations with a deadline of opening in Summer 1971.
As we know, the line (minus Pimlico station) opened on 23rd July 1971.
On opening, it was the first new section of Underground to open south of the Thames since the extension of the Nothern line from Clapham Common to Morden in 1926.
Images from The Brixton Extension of the Victoria Line, published by the London Transport Executive.