The experience of passengers using underground transport can be a familiar one for those who use it regularly, or a novel one for visitors from places where stations are always above the ground. But the actual processes involved in digging tunnels are rather more esoteric.

Among the issues not always appreciated by those not involved in construction is the sheer volume of material that needs to be removed when excavation takes place, for which a reliable conveyor belt needs to be installed to ensure progress is smooth.

As an example of this, the excavation of tunnels and underground station boxes for Crossrail produced millions of tonnes of material. The project made good use of this, with three million tonnes used in landscaping to create a new wetland nature reserve at Wallasea Island in Essex.

Crossrail was the most recent major tunnelling project to add to London’s transport network, with the most recent on the Underground itself being the Northern line extension, which opened in 2021.

A New London Tunnel – But Not The Bakerloo Line

This added to the relatively low numbers of Tube stations south of the Thames, but the prospect of more recently suffered a blow when the government’s recent announcement of transport funding for various projects did not include new cash for the proposed Bakerloo line extension.

It was no accident that this happened, as the government is prioritising transport projects elsewhere in England, mindful of the common gripe that the north and Midlands have far less money spent per capita on transport.

However, one project in London does have momentum, and this will involve a new tunnel. The proposed Docklands Light Railway (DLR) extension from Gallions Reach to Thamesmead via Beckton Riverside is about to go to a public consultation.

The plan would involve a new tunnel under the Thames, which would be the third on the network. The previous tunnel crossing was the link to Woolwich Arsenal, which was completed in 2009. The first was the line to Lewisham, which includes a tunnel between the Isle of Dogs and Greenwich, with two underground stations.

Part of the consultation will involve seeking public views on the location of stations, so it remains to be seen if any of these will be underground as well.

A Long Tradition Of Tunneling Under The Thames

However, if the proposal does go ahead, it will be the latest transport tunnel in east London, which, between 1825 and 1843, saw the construction of the world’s first ever tunnel under a navigable river, the Thames Tunnel between Wapping and Rotherhithe.

That tunnel used to be part of the London Underground’s East London line, before then being incorporated into the Overground, which means an Underground line that was partly over ground is now part of an Overground line that is partly underground.

For a rail line to have subterranean stations while not actually being classed as an Underground is nothing new, of course. The Elizabeth line is still classed as a mainline railway, as is Merseyrail in Liverpool and the sections of mainline rail passing through subterranean stations in Glasgow, quite separate from the Subway.

The DLR, however, may now join the Tyne and Wear Metro in being something of a hybrid system of underground and overground, although the Metro does not use any tunnels to cross the Wear or Tyne, the latter river being crossed by a bridge between its steep banks to link the underground tunnels and stations in Newcastle and Gateshead.

Fewer Tunnels As Money Heads North

No new tunnels will be included in the latest Metro extension, as it involves reusing the old railway track beds to connect Washington to the system.

The same is true for the extensions to existing tram systems in the West Midlands (across east Birmingham) and the Manchester Metrolink, or the long-awaited arrival of a tram system for Leeds (and Bradford). Bristol may be next for a surface metro system, but former mayor Marvin Rees’s dream of an Underground is dead.

Indeed, the only new tunnelling might involve the planned high-speed line between Manchester to Liverpool, partly because it will connect with the existing subterranean stations in the centre of the latter city.

All this extra funding for such projects outside London irked London mayor Sadiq Khan, who complained that: “The way to level up other regions will never be to level down London”. Others, however, argue that London has been getting the lion’s share of transport spending for too long.

While all this means fewer tunnels anywhere and certainly one less in London as the Old Kent Road is denied a chance to shake off its negative Monopoly board stereotype, there is still set to be one new project in the capital. No matter where else in Britain may get the money now, it seems there is always enough to dig another under the Thames.