Each time an epidemic of bubonic plague hit London between the 14th and 17th centuries, about 20% of the capital's population was wiped out. This led to graveyards and cemeteries becoming overcrowded and the need to bury victims of the plague in mass graves. The London Underground has often been cited as being built over or through these plague pits, but the story of these mass graves is far more interesting than that.
Two major plague epidemics swept through London between 1348 and 1665. The first, which many know as 'The Black Death', reportedly killed around half of London's population, while the second, 'The Great Plague', saw 100,000 deaths in 1665.
One of the most pervasive myths about the victims of these plagues is that, as parish cemeteries began to fill up, their bodies were buried haphazardly all over London - and they still reside there under the London Underground's tube network.
That myth even suggests that London's curving, meandering Underground network was specifically built around these plague pits.
A comprehensive report by Amanda Ruggeri for the BBC in 2016 unravels this mystery and reveals that this is most likely not the case. Plague pits are rare, mostly because in the time of the plague, Londoners clung to their routines for comfort.
Ensuring people were buried correctly was one of these routines and so the ritual was carried out in the sacred cemeteries by the churches of London. However, as the London Underground and rail network has continued to expand, construction crews have unearthed mass graves with plague victims inside.
The idea of a 'plague pit' conjures up images of bodies being thrown into the ground and soiled tipped over them quickly, in fear that the plague would spread further. But that doesn't mean that - as London's Underground has continued to expand with the new Crossrail project - construction crews haven't run into burial sites. Indeed, in 2015, the team working on the Crossrail project uncovered a mass grave around Liverpool Street station that contained some 3,500 skeletons.
Most of these were buried individually, as the site was the location of a 17th century burial ground, but they also found 42 individuals who had seemingly been buried together in a single pit. This mass grave was the first ever in the UK to be tied to the Great Plague of 1665.
Yet, although the bodies were found heaped together, archaeological findings showed that they were still buried in individual coffins that had been stacked on top of each other. Even in their despair, the Londoners seemed to hold onto the ritual of burial - and the idea of the 'plague pits' affecting the London Underground seems rather far-fetched.
It's an interesting and gruesome idea that the earth of London is filled with skeletons - but morality and legalities prevent the London rail network from ever passing through these ancient sites without licence or reason. Moreover, several times in the past, large-scale projects have been undertaken to relocate corpses to alternate locations across London, as is the case with the graveyard at St Pancras Old Church.
So if you've ever heard the notion that the London Underground is buried on top of the graves of plague victims - it's not exactly true,