Mystery of the Crossrail skulls

MOLA team

We teamed up with the University of Southampton to answer the centuries old question ‘why are so many Roman skulls found in the Walbrook valley?’ Bringing together archaeological evidence and oceanographic testing, we have shown that natural forces, erosion from the Walbrook River, can be credited with causing this mysterious phenomenon.

The findings are revealed in ‘Mystery of the Crossrail Skulls’ produced by True North Productions, airing on Channel 4, on Sunday the 24 April, at 8pm, which explores a range of theories, including long-lost rituals.

The Walbrook skulls debate has roared for centuries. Their presence has been known since the 1200s and numerous findings of disarticulated Roman skulls were recorded in the 19th century, including those found in a sewer in 1839 on Blomfield Street. 

The theories as to their origin are many and various and include: decapitated victims of Boudica’s sacking of London, trophy heads collected by Roman soldiers and a continuation of the Iron Age ‘cult of the head’. The systematic excavation of a series of sites in the Walbrook valley, including most recently our excavations at Liverpool Street for Crossrail, has given our archaeologists an opportunity to methodically study these remains in the context of the Roman landscape.

The Walbrook Valley was a watery landscape in the Roman period and the river had a network of streams that flooded seasonally. The Romans tried to manage the water and our archaeological excavation revealed a number of attempts to reclaim land. Today, the Walbrook River runs entirely underground and leads into the Thames by Cannon Street.  

Whilst studying the cemeteries set up by the Romans outside the city walls, our archaeologists found burials close to the banks of the streams that were partially washed away by overflowing water. Working with researchers from Ocean and Earth Science at the University of Southampton, we have been able to test how this fluvial (river) erosion carried the human remains downstream. Placing a replica skull and long bone in a long flume that replicates the flow of the Walbrook River, it confirmed that the shape and buoyancy of the skulls meant that they bobbed or rolled over long distances, whereas long bones, such as leg bones, sunk with little movement.

Analysing the skulls, our osteologists have identified a number of characteristics that corroborate this model, these include: shiny polished skulls where they sat in running water, pitted skulls where the gravels of the water bed chipped at the bone, and discolouration, staining and tide marks where the remains were waterlogged. Our osteologists also recorded a lack of jaw bones, which indicates that the skulls came to rest when they were already disarticulated from the rest of the body.

Using a flume filled with gravel, mirroring the conditions of the Walbrook River, researchers Charlie Thompson and Samuel Griffith simulated what effects the impact of the gravel had on animal remains, chipping away at the bone to create a pocked-marked surface.

We have published further research into the effects of fluvial erosion in The Upper Walbrook valley cemetery of Roman London, which is available to buy at

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