The Bakerloo line does not swerve around a plague pit

Ask around and someone will tell you the Bakerloo line kinks sharply south of Elephant & Castle because Victorian engineers swerved the tunnel to avoid a plague pit, a mass grave of 1665 victims nobody wanted to disturb. It is one of the most repeated stories about the network, and it has a tell hiding in plain sight: ask a different person and the same explanation gets attached to a sharp curve on the Piccadilly line instead, or the Central line, depending on who is telling it.

A story that moves between lines and never quite lands on documented evidence is usually folklore rather than engineering history, and this one is no exception. The real explanation for why deep tube tunnels bend the way they do is duller than ghosts and considerably better documented: it is about who owned the ground above, not what was buried under it. You can check the shape of every line yourself in the London network explorer or by playing the London guessing game.

The legend, as usually told

The version popularised by Catharine Arnold's book Necropolis: London and Its Dead holds that tunnellers building the Underground kept hitting, or deliberately routed around, the remains of plague victims buried during the Great Plague of 1665. Arnold later described the claim as anecdotal rather than something she had traced to a primary source, which is a fairly large admission for a story that gets repeated as settled fact on almost every London ghost tour.

The legend survives because it is a satisfying answer to a real, observable thing: several tube lines do curve sharply in places, and a sharp curve without an obvious cause invites a story. Plague pits are a good story. They just are not the cause of these particular curves.

Why it doesn't hold up

The folklore researcher Scott Wood has pointed out that there is no archival record of tunnelling work, including the digging of the Victoria line in the 1960s, ever disturbing a plague-era mass grave. Victorian and twentieth-century engineers surveyed ground carefully before boring through it; a genuine encounter with a mass grave during construction would have been the kind of thing that made contemporary newspapers, not something quietly avoided and never written down.

There is also the consistency problem. Real engineering constraints tend to explain one specific curve at one specific location. A plague pit story that can be told about the Bakerloo, the Piccadilly or the Central line, depending on the teller, is behaving like a floating explanation looking for a curve to attach to, not a documented incident.

What plague burials actually looked like

Popular imagination pictures 1665 London riddled with secret pits waiting to be rediscovered by anyone with a shovel. The reality is more mundane: most plague victims were buried in existing parish churchyards or in the grounds of local pest houses, the isolation hospitals set up to keep the sick away from the rest of the population, rather than in a scattering of undocumented mass graves across the city. There are far fewer genuine plague burial sites than the myth requires.

When burial sites of this kind have turned up during major infrastructure projects, the pattern is the opposite of secrecy. Crossrail's excavation of the old Bedlam burial ground near Liverpool Street and the Black Death find at Charterhouse Square were both investigated archaeologically, recorded and reported on, because that is what happens when construction meets a genuine burial site in modern London. Nobody quietly reroutes a tunnel and says nothing; the finds get published.

The real reason tunnels curve: Victorian property law, not fear of ghosts

The actual cause is a quirk of nineteenth-century property law. A company boring a tube tunnel had an automatic legal right to run it under a public road without paying the landowner anything. Tunnelling under private property, on the other hand, meant paying a wayleave to whoever owned the freehold above, floor by floor, all the way to the surface. Engineers therefore did the obvious commercial thing: they kept their tunnels under the street plan as closely as they could.

London's streets do not run in straight lines, and neither do tunnels built to stay beneath them. Every time a road bends, forks or meets another at an angle, a tunnel following it has to bend too. That is where the sharp kinks on lines like the Piccadilly and the Northern actually come from: a strip of cheap legal right-of-way traced under a street pattern designed centuries before anyone imagined a railway underneath it.

Rivers, sewers and foundations: the other real culprit

Where a tunnel does leave the line of the street, the more likely reason is something else entirely ordinary: an existing sewer, a buried river such as the Fleet, or the foundations of a building too expensive to tunnel beneath without extra work. All three turn up constantly in the engineering history of the network, are well documented in construction records, and require no folklore to explain at all. Compared with those, a mass grave nobody ever found is not a competing theory so much as a good story that outlived the facts.