Timeline of the Chilterns

The Chilterns has a rich and varied geology and history  – from prehistoric times, when warm, shallow seas laid down the distinctive chalk of the area, through Bronze Age settlements, Victorian industry, right up to today’s working landscape.

The skeleton of the Chilterns Hills is made up of layers of chalk. This landscape has been shaped by geological forces, nature and people throughout the ages. Our timeline guides you through what has changed and what remains today, and how these features affect the wildlife, industry and environments we now see.

To see some of our geology and history in action, browse our interactive map for ideas about great days outs and places to visit. Or take a look at our Places to visit section for more inspiration.

The Chilterns' timeline

Around 100 million years ago, when dinosaurs ruled the Earth, the area that would eventually become the Chilterns was submerged under a clear, sub-tropical sea. Soft, white limestone was slowly laid down under this sea as the remains of millions of coccolithophores (microscopic algae) fell to the seabed. Warm seas covered the area for more than 20 million years, and the chalk beds grew thick.

The famous flint of the Chiltern Hills is a type of silica that was also formed during this period. Silica-rich organisms like sponges and diatoms died and fell to the seabed, their silica replacing chalk that had dissolved or been burrowed away. Eventually, flint nodules formed in these gaps.

The same tectonic movements of the Earth’s crust that formed the Alps caused the chalk to buckle and fold, and these sedimentary rocks emerged from the receding sea. Over millions of years, wind and water eroded the soft limestone that was laid during the age of the dinosaurs, leading to the formation of the steep chalk scarp and shallower dip-slope that can be seen today.

The Earth went into the Quaternary Ice Age around 2.58 million years ago. With ice at the polar caps, scientists still consider us to be in it now! Throughout this period, there have been glacial and interglacial periods – times when the ice has advanced and times when it has receded, like now.

During these glacials and interglacials, sand, gravel and clay were deposited in layers over the Chilterns’ chalk by glaciers, melt waters and wind. For several thousand years, Chilterns was a tundra and the chalk frozen, making it impermeable to water, and allowing surface water to erode the rock and create valleys.

The earliest current record of human occupation in the Chilterns comes from flint fragments that date from the Palaeolithic Period. There have been nationally notable finds of flint tools that provide evidence of Neanderthal hunter-gatherers in the area.

After the last glacial maximum (the last time the ice sheets were extensive), permanent occupation began in the Chilterns. As the ice retreated, sea levels rose, eventually cutting Britain off from Europe. Vegetation returned and human activity was often focused along river valleys. Finds of Mesolithic flint tools are widespread – likely used by nomadic hunter-gatherers to catch and eat red deer, aurochs (large wild cattle) and fish.

During the Neolithic Period, hunting and gathering was replaced with new farming practices. Woodlands were cleared for arable farming and the keeping of domestic animals, and people gradually became more settled. The chalk scarp, with its access to light, easily tilled soils and springs of clean water would have been a focal point of settlement.

Evidence of Neolithic life in the Chilterns includes the barrow (burial mound) at Whiteleaf Hill.

During the Bronze Age, people increasingly used metal tools and weapons, rather than stone, and semi-nomadic farming gave way to permanent settlements. Some ancient Chilterns’ routeways, such as the Ridgeway, date from this time and the building of hillforts began to transform the landscape.

Some of the most striking prehistoric monuments in the Chilterns are a series of hillforts dating from the Iron Age and sited in strategic locations along the scarp or overlooking river valleys.

Around this time, the Icknield Way developed along the chalk ridge; stretching from Wessex to East Anglia, it is claimed to be Britain’s oldest road, although there is little in the way of solid evidence for this. Throughout time, drovers, traders and invaders have all walked or ridden this route over higher ground, which would have been drier and less wooded.

Evidence of Roman occupation, including the remains of villas, iron works and pottery kilns, has mainly been found on the dip-slope to the east of the scarp. The nearby town of Verulamium (now St Albans) was a major Roman settlement, with roads radiating out from it. The Roman road of Watling Street headed north-west along the Ver Valley – now the route of the A5. Akeman Street headed west, following the Bulbourne Valley (now the route of the A41 and A4251).

By the beginning of the 5th century AD, Roman influence had waned as the Empire had begun to crumble. Often called the ‘Dark Ages’, this period was actually a very busy time in Britain. The first written reference to the Chilterns is found in a 7th century document, the Tribal Hidage, which refers to the ‘people of Chiltern’. It appears that the Saxon estates were gradually divided into smaller parishes, a pattern still recognisable today. The Danelaw, the 9th century boundary between Viking lands and Wessex, ran through the Chilterns at Luton.

The Domesday Book of 1086 shows the Chilterns to be less densely populated than the surrounding vales. Yet, the patchwork of villages, small fields and woodlands, separated by hedges and earth banks is very familiar. Much of the Chilterns’ landscape as we know it was in place by the end of the Medieval Ages.

During this time, a clear distinction developed between villages at the scarp-foot, which had an ‘open field’ system, and the villages of the dip-slope, where the land was already parcelled-up into ‘closes’ that were controlled by individual landowners or tenants.

The War of the Roses ended, and a new state religion was ushered in. Political stability enabled farming to prosper, and Chilterns’ food and fuel were supplied to a growing London.

Parliamentary enclosure saw open fields divided up into regularly shaped fields, many of which are still visible in the region today. However, in the dip-slope areas, enclosure was limited to some division of common land and the older, smaller, co-axial field patterns remained intact.

Arable farming dominated the era as metropolitan demand increased. Early maps show the extent of woodland that we now consider to be ‘ancient’ (pre-1600; such as Penn Wood in Buckinghamshire), and cherry orchards increased as pickers could travel from London.

The Industrial revolution took hold during the Georgian era, transforming Britain and the world with innovation and invention. Improved transport routes in the 18th and 19th centuries had a major impact on the Chilterns, both directly as landscape features, but also through the opening up of new markets. These routes followed the easiest passages through the hills: the arterial valleys.

Several of the main roads through the Chilterns have their origins as turnpikes. These toll roads were constructed from around 1750 onwards in response to the increased volume of wheeled traffic. They enabled more goods to be moved between rural areas and towns. The Old Toll House can still be seen when heading north out of Great Missenden.

The Grand Union Canal was constructed in the 1790s to connect London and Birmingham. Cutting through the Bulbourne Valley, the canal enabled bulky goods from the Chilterns, such as firewood and hay, to be supplied to London. Coal eventually overtook wood as the main fuel in London, however, leading to a decline in traditional woodland management, such as coppicing.

As the wood-fuel industry declined, the Chilterns’ chair-making industry took off, leading to the plantation of beech trees. This has resulted in one of the Chilterns’ most distinctive landscape features – its extensive beechwoods. While on the river, the industrial revolution saw Victorian mills for flour, cloth and paper multiply.

The improved road network also led to the growth of country estates in the Chilterns. Some already existed as landed estates and deer parks (such as Stonor Park), but others were created by people who wanted a country estate at a convenient distance from London.

Finally, the building of a network of railways through the Chilterns between 1839 and 1906 transformed the local economy and led to the rapid and extensive expansion of towns and villages.

During the 20th century, trade, production and innovation continued and increased, despite two major world wars. Yet, post-war agricultural intensification caused the loss of some local landscape features, including hedgerows and habitats; and the decline of land-based employment, skills and crafts followed.

In the Chilterns, the 20th century saw the construction of new communications and infrastructure, including the M40, pylons and transmission masts. A number of military establishments grew up and an increasing proportion of land was turned to recreational use, particularly as golf courses.

In 1965, the Chilterns was designated as an Area of Outstanding Beauty (AONB) in recognition of the importance of its landscape and wildlife features.

Today, population growth is still adding pressure on our protected landscape, but there is growing environmental awareness, new technologies are being developed to help combat threats, and new people are keen to explore, learn and protect the countryside.

Chilterns ANOB
Chilterns ANOB

Visit the Chilterns

Quintessential English countryside, an impressive selection of pubs and restaurants, and historic market towns, the Chilterns AONB has it all.
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Bookable experiences

We have carefully chosen our most immersive and memorable Chilterns Countryside Experiences to share with you here. Choose from Active Countryside, Chilterns Food & Drink, Countryside Learning and Chilterns Sightseeing. All are bookable online.