What did the Romans ever do for us (if they didn't build our roads)?

Archaeologists have found Britain's oldest properly engineered road, and the discovery could change the way we look at a key aspect of British history. Now, many of the country's key A roads – long thought to be Roman in origin – could now turn out to be substantially more British than scholars had thought.

The discoveries, in Shropshire, suggest that ancient Britons were building finely engineered, well-cambered and skilfully metalled roads before the Emperor Claudius's conquering legions ever set foot in Britain in the middle of the 1st century BC.

"The traditional view has often been that Iron Age Britons were unsophisticated people who needed to be civilised by the Romans," said Tim Malim, an archaeologist from the UK environmental planning consultancy, SLR, who co-directed the Shropshire excavation. "It's an attitude that largely has its roots in the late 19th century when Britain saw itself very much as the new Rome, bringing civilisation to the rest of the world." The Shropshire road was built, the archaeologists believe, up to 100 years before the Romans conquered Britain. The archaeologists suspect that the road may have been 40 miles long.

So far, they have found two sections, totalling 400m, but their alignment suggests that the road connected two key political centres of the Iron Age tribal kingdom of the Cornovii, the Cornovian "capital", the Wrekin hill-fort near modern Telford, and Old Oswestry hill-fort, near modern Oswestry.

The discovery of the road, revealed in the BBC History Magazine, is for the first time demonstrating the sophistication of British Iron Age cross-country road construction.

First a brushwood foundation (made of elder) was laid down. Then a layer of silt was placed on top of the brushwood, and finally a layer of cobbles was set into the silt to provide a good surface. A kerb system, kept in place by timber uprights, was even constructed to prevent the Iron Age highway slumping. The road was regularly maintained, and resurfaced at least twice during its life.

The excavations, funded by the UK's largest building materials company, Tarmac, have also provided remarkable information about the wheeled traffic using the Iron Age highway.

Prior to the final phase of use, there is no evidence for heavy wheeled vehicles. But in the very late Iron Age, there seems to have been a dramatic increase in heavy traffic, with evidence of the deep ruts caused by large wheeled vehicles, almost certainly carts carrying agricultural produce. The rut evidence suggests that the vehicles had axle widths of 1.9m and wheels which were 12 to 17cm wide.

The findings are likely to prompt archaeologists in other parts of Britain to re-examine some more straight-as-a-die typically Roman-looking roads to see whether they too were originally British native Iron Age ones.