City of London

The Square Mile sits on two thousand years of continuous occupation — from Londinium, Rome's second greatest British city, through Saxon Lundenwic, medieval guild halls, and the Great Fire of 1666.

History & Significance

The City of London — the Square Mile — is among the most archaeologically layered places in Britain. Every building project drives through stratigraphy that runs from the modern era down through post-medieval warehouses, medieval lanes, Saxon occupation, and into the deep deposits of Roman Londinium. Almost nowhere else in the country does so much recorded history sit so densely on top of so little ground.

Londinium was founded shortly after the Roman invasion of 43 AD, most likely as a commercial and administrative centre rather than a legionary fortress. Within twenty years it had grown into the largest town in Roman Britain, with a forum, basilica, amphitheatre, governor's palace, and the longest Roman bridge in the province crossing the Thames at what is now London Bridge. Boudica burned it to the ground around 60–61 AD — a burnt horizon of clay and ash found repeatedly in excavations across the City. It was rebuilt, expanded, and eventually enclosed within a stone wall that still stands in fragments at Tower Hill, Noble Street, and the Barbican.

After the Roman withdrawal in 410 AD, the walled city was progressively abandoned. The Saxons settled outside the walls, in an area called Lundenwic centred on the Strand, and the Roman city became a landscape of ruins, fields, and occasional occupation. It was Alfred the Great who reoccupied Lundenburh — the fortified walled city — in 886 AD as a defensive response to Danish raids. From that point the City's continuous occupation begins again, and by the time of Domesday in 1086 it was England's largest and wealthiest urban centre.

The medieval City was a dense, governed, guild-regulated community of merchants, craftsmen, and ecclesiastical institutions, with over a hundred parish churches in its single square mile. The Great Fire of September 1666 destroyed four-fifths of the City in four days, and it was rebuilt largely to its medieval street plan — which is why the City's streets still bear names like Cheapside, Poultry, Cornhill, and Threadneedle Street, each recording the trade or commodity once sold there.

Londinium was not a planned military colony but a civilian town that grew rapidly because of its geography. The Thames at this point was tidal but crossable; the two gravel hills on the north bank — Cornhill and Ludgate Hill — offered well-drained, defensible ground. Within a generation of the conquest the settlement had grown large enough to serve as the effective capital of the province, replacing Camulodunum (Colchester) as the administrative centre after Boudica's revolt.

The Boudican destruction layer — a band of burnt daub, tile, and charred goods — is one of the most reliably identified stratigraphic markers in London archaeology. Finds of melted Samian ware, burnt grain, and structural debris from this horizon have been recovered from excavations across the City for decades. Above it, the rebuilt Londinium expanded dramatically: the forum-basilica complex near Gracechurch Street was the largest in Roman Britain, larger than that at any other provincial town. The amphitheatre, discovered beneath the Guildhall Yard in 1988, could seat around 7,000 people.

The Roman city wall, built in the late second and early third centuries, enclosed an area of approximately 330 acres. It was constructed of Kentish ragstone brought upriver from quarries near Maidstone, and its foundations survive beneath many parts of the modern City. Above ground, the most substantial surviving sections are at Tower Hill — where the medieval and Roman phases can be distinguished by the tile bonding courses — and in the Barbican, where a section preserves both the Roman core and the medieval heightening.

The medieval City was governed by its own institutions — the Corporation of London, the Lord Mayor, the aldermen, and the livery companies — with a degree of autonomy from the Crown that no other English town possessed. This self-governance was underwritten by commercial wealth. The City's merchants controlled much of England's overseas trade, and the great livery companies — the Mercers, Grocers, Drapers, Fishmongers, Goldsmiths, and the rest — were among the most powerful non-royal institutions in the country.

The street names of the medieval City were descriptive: Cheapside (from the Old English ceap, meaning market) was the main commercial thoroughfare. Off it ran Bread Street, Milk Street, Wood Street, and Honey Lane. Poultry extended eastward from Cheapside; the Shambles (meat market) lay to the west. Lombard Street recorded the Italian bankers who settled there from the thirteenth century. Goldsmiths' work was done around Cheapside — and the density of precious metal work recovered from this area in archaeological excavations reflects that concentration.

The hundred-odd medieval parish churches of the City were reduced by the Great Fire to about fifty, which were then rebuilt to Wren's designs. A further reduction in the Victorian era left the thirty-nine Anglican churches that survive today. Each church sits on a medieval foundation, and several preserve pre-Conquest dedications: All Hallows by the Tower is regarded as the oldest church in the City, with Saxon fabric and a Roman pavement in its crypt.

The Great Fire of London began on the night of 2 September 1666 in a bakehouse on Pudding Lane, and burned for four days and nights. It destroyed 373 acres within the City walls, 13,200 houses, 87 parish churches, the Royal Exchange, Guildhall, and St Paul's Cathedral. The death toll was remarkably low — perhaps a dozen confirmed deaths — because the fire moved slowly enough during daylight for most people to evacuate.

The fire horizon of 1666 is as recognisable in London's archaeology as the Boudican horizon of 60–61 AD. Layers of burnt tile, charred timber, and melted glass mark the boundary between medieval and post-medieval deposits across the City. Objects recovered from the fire layer — pewter tankards, clay pipes, pottery, and occasionally coins — are among the most commonly encountered finds in City excavations.

The rebuilding after the Fire was rapid and largely followed the old street plan. Wren's opportunity came with the churches: he rebuilt 51 of the destroyed churches over the following decades, as well as the new St Paul's Cathedral, completed in 1710. The rebuilt City was brick and stone rather than timber-framed — this is the City that the Victorian era then substantially rebuilt again, leaving the Street of Gold in its current form almost entirely a product of the late nineteenth and early twentieth centuries, but following lane lines established in the Saxon and medieval periods.

See the full research report for City of London

Scheduled monuments, PAS archaeological finds, Domesday records, geology, Roman roads, historical literature — the same report Aubrey generates for paying customers, free to read.