In 1175, Alain de Lille wrote “mille viae ducunt homines per saecula Romam” (a thousand roads lead men forever to Rome) in his book Liber Parabolarum.   Geoffrey Chaucer used a version of: ‘All roads lead to Rome’ in his 1391 text A Treatise on the Astrolabe.

There is some truth in the saying, for many of the system of roads built by the Roman Empire met at the Milliarium Aureum (Golden Milestone) in Rome.

At its peak, the Roman road system spanned roughly 186,000 to 250,000 miles  across three continents. This network connected over 113 provinces, stretching from the hills of England all the way to the Tigris-Euphrates river system in Iraq, and from the Danube River down to the Sahara Desert in North Africa.

Of these, about 50,000 miles consisted of paved, hard-surfaced stone highways used for rapid military deployment. However, the majority of the network consisted of unpaved, gravel dirt paths, subject to the vagaries of seasonal temperatures and weather. Even the major roads were subject to damage by frost, for instance, and required regular maintenance.

The Decay Timeline of an Abandoned Roman Road:

• Years 1–20 (Pristine): The road remains in perfect condition. Because the top slabs are fitted tightly together and sloped to shed water, rain simply runs off into side ditches.
• Years 20–70 (Slow Erosion): Without teams clearing them, drainage ditches fill with silt, weeds, and debris. Water begins to pool on the road surface. In colder climates, this water seeps into tiny cracks between stones, freezes, expands, and slowly begins to dislodge the heavy paving slabs.
• Years 70–100 (The Surface Breaks): Over a century of tree roots growing under the stones and heavy rainstorms finally cracks the top layer. Once the top stone skin is breached, water reaches the interior sand and gravel layers, washing them away and causing potholes.
• Years 100–1,500+ (The Foundation Survives): Even when the top layer is completely choked by soil and forest, the deep foundation—made of massive rocks embedded in mortar and volcanic concrete—refuses to rot.

After the end of the Roman Empire, the absence of the regular maintenance program meant that this deterioration started – worse in some areas than others, partly depending on climate, but also because some local authorities did attempt to maintain the surfaces as best they could.

However, about a century after the end of Empire, word came from remote Scotland that a certain John McAdam had invented a form of pavement for the rugged roads in that country, which could easily be adapted to resuscitate the roads of the Old Empire.  His roads were built with a compacted subgrade of crushed granite or greenstone designed to support the load, covered by a surface of light stone to absorb wear and tear and shed water to the drainage ditches.

Through the course of the next hundred years (ie by the time of Captured in Amber) the main transit roads in continental Europe had been converted to or built using the McAdam process, or a variation devised by Thomas Telford, who dug down to locate the heavy, surviving Roman stone foundation slabs, levelled them out, and used them as a sturdy base, before placing smaller stones on top.

John McAdam completely rejected this idea. His core principle was that heavy stone foundations are a road’s worst enemy. He believed that the soil carries the weight: the native soil underneath can support any vehicle, provided it is kept completely dry, while if you put flexible, crushed stone over a rigid, solid Roman stone base, heavy carriage wheels will compress the top stones against the hard bottom stones. This acts like a hammer and anvil, rapidly grinding the road surface into dust from the inside out.

By the time of the book, macadamisation in its two varieties had restored most of the roads throughout the Continent, but was generating large quantities of dust while eroding under heavy traffic, just awaiting, in another dozen or so years, Edgar Purnell Hooley to accidentally discover that an industrial barrel spill of tar mixed with waste slag from an ironworks created a smooth, dust-free, and solid surface. He would come to patent this process as ‘tarmacadam’.