Much has been written about Kent's Roman roots and the empire's legacy continues to shape much of the county today.

From the original landing at Richborough, near Sandwich, to the remains in Canterbury, Dover, Lullingstone and Reculver, even many of our main roads still follow the straight paths of the invaders more than 2,000 years ago.

It has also long been known that much of the building stone which built Roman London through to the mid-3rd century AD was ragstone from the upper Medway Valley.

Dr Simon Elliott is a well known figures in archaeological circles in the county.

Having moved to East Farleigh, near Maidstone in 2004, he became increasingly interested in this industry, completing a PhD at the University of Kent in Canterbury which addressed the issue of where the exact quarries were, and the economic model behind how the industry was operated.

This included an examination of whether the Roman military, in the form of the Classis Britannica regional navy, which controlled the waters of the English Channel, participated in its running.

His research was recently published by British Archaeological Reports as Ragstone to Riches: Imperial Estates, Metalla and the Roman Military in the South East of Britain During the Occupation.

In this article, Dr Elliott sets out his new theories to encourage interest in this fascinating aspect of the story of Roman Britain, when Kent was the industrial heartland of the province.

Ragstone is grey-green sandy limestone from the Hythe Beds in the Lower Greensand geological formation - which we today identify as the Weald.

It was utilised across the south east of the province of Britannia - the Roman name for Britain - in huge quantities, either as dressed facing stone, in-fill rubble or to create hard road surfaces, principally because it is hard-wearing but also workable.

The sheer scale of this industry is particularly striking, with enormous quantities of stone utilised.

The main outcrops, then as now, are near Folkestone, around Maidstone and near Sevenoaks. That used by the Romans came from quarries near Maidstone

I began my search to determine where the actual quarries were located by looking at the first good quality sequence of maps for the upper Medway Valley, namely those of the 1797 Ordnance Survey.

My focus was initially industrial scale quarries which by then were extinct and overgrown.

I then looked at the Roman-period archaeological evidence surrounding the candidate sites which indicated some kind of industrial activity, and settlement and transport routes associated with this.

I finally physically examined those accessible, in one case actually finding the mason’s marks on exposed ragstone surfaces made by a skilled Roman stone worker.

Overall, this methodology enabled me to identify the five candidates which I argue were the quarries which made up this metalla – the Roman name for such an extractive industry.

These were at Allington, Boughton Monchelsea, Dean Street, Quarry Wood in West Farleigh and Teston.

The first is on the modern tidal reach of the River Medway, though in the Roman period this was likely further downriver around Snodland. The other four are well above the tidal reach.

The industry began very early in the Roman occupation, there being evidence that stone was being quarried here from around AD 50 for use in the first forum in London.

This means the Romans would have been aware of this resource well before the AD 43 Claudian invasion at Richborough.

The industry quickly developed into an industrial scale activity.

This was to fulfil the booming demand for building stone as the new stone-built urban environment developed in the region, also facilitating the construction of new villa estates and roads across the area.

Demand peaked in the late second and early third centuries AD. This was when construction began of the region’s first fortified wall circuits.

The best example is the 3.2km land walls of Roman London built by Septimius Severus in the late AD 190s.

With regard to these land walls in London, some statistics are particularly useful to appreciate the scale of the undertaking.

The walls included more than one million squared and well dressed ragstone blocks needed for the facing, an overall ragstone volume of 35,000 cubic metres, requiring 420,000 man days to build and 1,750 voyages of medium sized merchant ships to transport the stone the 127km from the quarries to London.

Ragstone from this metalla was widely used elsewhere in London.

Examples include the second iteration of the amphitheatre, the later basilica and forum (the largest stone built structure north of the Alps during the occupation), the governor’s palace, three public bath houses and a wide variety of other public buildings.

Ragstone was also used to build many private dwellings.

The industry survived to the mid-3rd century AD when construction using ragstone – at least in terms of new material – finished.

After that any grand public buildings in the south east used other types of material. This included much reused stone from demolished mausoleums and public buildings.

I argue the sheer scale of the upper Medway Valley quarrying industry is one of the key pointers to the presence of the state in the form of the military in their operation.

For example, the surface areas of the actual quarries, vast in scale, were 61,600m-squared for that at Allington, 54,600m-sq for that at Boughton Monchelsea, 356,400m-sq for that at Dean Street, 215,000m-sq for that at Quarry Wood and 35,830m-sq for that at Teston.

These were clearly industrial in the modern sense of the word. That at Dean Street was comparable in size to the largest metalla across the entirety of the Roman Empire.

Further evidence for the presence of the military helping run the industry comes from the maritime nature of the transport of the extracted materials to London down the River Medway and, in the case of Roman London, up the Thames Estuary and River Thames.

Hard data exists to support this in the form of the enigmatic Blackfriars 1 vessel medium sized transport vessel found on the bed of the River Thames in 1962.

When it sank it was carrying a load of 26 tonnes of Kentish ragstone in its hold.

In terms of regional land transport at the time, this also backs up the view that the military was involved in the running of the ragstone quarries.

For example the Roman Rochester to Wealden road, for much of its length today the route of the A229, linked the north Kent coast with the major iron working sites in the eastern/coastal Weald.

Along the way it passed very close to the ragstone quarries of the upper Medway Valley, and indeed may be directly linked to them by a possible spur road now under investigation.

The Wealden Roman iron industry, another massive regional metalla, has long been associated with the Classis Britannica regional navy through archaeological evidence.

Put together, the maritime nature of the mode of transport for the ragstone, and the close proximity to the seemingly linked Classis Britannica run Wealden iron industry, indicates to me that the regional navy was also involved in the upper Medway Valley ragstone quarrying industry.

Indeed it may be they were one linked metalla run by the navy.

Looking at analogy, this also backs a role for the military here.

For example the Classis Germanica regional navy along the River Rhine is well known for its quarrying activities along the river and its tributaries.

Evidence of the Classis Britannica carrying out quarrying activities also comes from even closer to hand, with for example the inscription at Benwell Fort on Hadrian’s Wall showing the regional fleet constructing a granary there.

Finally, anecdote also seems to show a military presence running industry in this region during the Roman occupation.

For example, there is certainly a synergy between the mid-3rd century AD ending of industrial scale ragstone quarrying in the upper Medway Valley, the similar ending of the Wealden iron industry, and the disappearance of the Classis Britannica.

The event which perhaps caused all three was known as the Crisis of the Third Century when the Roman Empire was wracked with economic and political instability.

When it finally emerged from this after Diocletian became Emperor in AD 284 the empire was very different from all that had gone before, and the two industries in Kent and the regional navy had all gone, never to return.

• Dr Simon Elliott is an historian and archaeologist based in Kent where he completed his PhD in 2017. He has published five books to date on Roman themes: Ragstone to Riches (on sale now, through BAR Publishing and available at Amazon), Sea Eagles of Empire about the Classis Britannica, Empire State which details the Roman military in their non-conflict roles, and Roman Legionaries.