110 - Chilterns : Description

Physical and functional links to other National Character Areas

Chilterns is one of several NCAs within a Chalk outcrop stretching from East Anglia to Dorset and the South Downs. To the north-east, the Chiltern escarpment lowers into the East Anglian Chalk. In the south-west, the escarpments of the Chilterns and Berkshire and Marlborough Downs face each other across the Goring Gap. From the north-west facing escarpment, the dip slope descends south-east into the London Basin. Here, the Chalk is overlain by younger bedrock.

The Chilterns scarp is prominent and offers panoramic views of the adjacent vales. Aylesbury Vale is especially visible from vantage points such as Ivinghoe Beacon. Across the vales there is inter-visibility with other elevated NCAs such as Midvale Ridge and Bedfordshire Greensand Ridge.

From the northern scarp, the rivers Flit and Ouzel (also known as Lovat) flow into the Bedfordshire and Cambridgeshire Claylands. Here they form part of the Anglian catchment. Along the remainder of the scarp, watercourses flow into the Upper Thames Clay Vales to feed the Thames catchment. The Thames flows through the Chiltern ridge at the Goring Gap to enter the London Basin.

Within the London Basin, the Chilterns’ natural groundwater and surface water flows are linked to those of the wider basin. The landscape also forms the larger of the two principal aquifers in the basin (the other being the North Downs). Infiltration in the Chilterns supports groundwater levels and quality in London’s confined aquifer. It also moderates the base flow in the Thames.

The Chilterns are linked into a modern transport network of motorways and railways radiating from nearby London. Outside London, major roads around Reading, Maidenhead, Slough and Aylesbury also link to the Chilterns. Long-distance historic routes now function as key recreation corridors: the Grand Union Canal, the Thames and the Ridgeway.

Distinct areas

• Thames Valley

The Chilterns today

The Chilterns are a distinctive outcrop of the Chalk, with a dramatic scarp forming the north-western boundary. From the long, north-west-facing scarp there are extensive, panoramic views over the adjacent vales. The dip slope falls gently to the south-east, cut by a series of branching valleys. The enclosed character of the valleys contrasts with the open plateau and long views from the scarp. Rising to just above 260m, the hills stretch from Oxfordshire to Bedfordshire in the north-east.

The area includes the lower-lying substantial settlements of Luton, Dunstable, Hemel Hempstead, Berkhamsted, Chesham, Amersham and High Wycombe. It is also crossed by sections of the M40 and M1 motorway corridors. The south-western boundary is formed by the River Thames. This belt of countryside is dominated by the river and its flood plain rather than by the hills.

While many dip slope valleys are dry, there are several chalk rivers flowing through others, such as the Chess. Springs and watercourses emerge from the foot of the scarp, such as the Ewelme Brook. Many of the watercourses are ‘bournes’ or ‘winterbournes’, which dry up near their source when groundwater levels are low. Many chalk streams receive treated discharges, often to counter low flows caused by abstraction. The presence of reliable water sources often determined the historic location of settlement. Canalisation, relict watercress beds, mills, sewage works, habitat enhancements and riverside green spaces catalogue a history of use and modification. They also attest to the significance of water in a chalk landscape.

The countryside of the Chilterns combines mixed agriculture with numerous ancient woodlands and hedgerows. Steeper ground is often characterised by small fields. There is a notable concentration of pre-18th-century fields (including assarts and co-axial fields) in Buckinghamshire and Oxfordshire.

There are localised concentrations of arable production in the north, around Luton, and in the ‘Ipsden prairie’ of Oxfordshire. Livestock farming is dominated by sheep and cattle. Grazing animals also help to conserve open grassland on historic downland. Meadows remain alongside watercourses but are rarely traditionally managed. Cherry orchards, once a widespread feature of the central belt, are now rare. Farmland supports a wide range of birds, including corn bunting, yellow hammer and grey partridge. Arable weeds are also important, such as prickly poppy and shepherd’s needle.

Woodland cover is extensive, making the Chilterns one of the most wooded lowland landscapes in England. Large woods, dominated by beech, are found on the plateau and as ‘hanging’ woods above the valleys; there are also small farm woodlands. Chilterns beechwoods (designated as SAC) are renowned for ‘cathedral-like’ qualities and bright autumn colours. Secondary woodland is found on once-open common land and downland. Elsewhere, many woods are ancient. Soaring above the woods and valleys, the distinctive forked tail of the red kite is now a common sight. Deer are often glimpsed in woodlands and fields.

Rare box woods on the scarp and habitat mosaics form locally distinctive features. At Hartslock Wood SAC, a species-rich area of chalk downland lies within a mosaic of beech and yew woodland. Aston Rowant SAC features an internationally important juniper population. Remnant areas of heathland, acid grassland and wood pasture are scattered across the plateau. These are often associated with common land and parkland on low-fertility soils. The scarp and some dry valley slopes are characterised by fragmented areas of species-rich chalk grassland with scrub. Colourful flowers feature during spring and summer, including the rare Chiltern gentian, pasque flower and orchids. Butterflies, including the restricted Duke of Burgundy and chalkhill blue, can also be spotted. In addition, there are a few small areas of rare chalk heath.

Dispersed farmsteads and hamlets are found on the plateau, with nucleated settlements in valleys and at the scarp foot. Some linear villages dating from the mid-19th century are associated with common land on the plateau. Many lower-lying settlements contain historic centres, often dating back to the medieval period. St Albans contains remains of the major Roman town of Verulamium. Historic, and some modern, buildings use local, traditional materials. These include flint, brick, clay tiles and occasionally thatch. Clunch, an impure and harder form of chalk, is sometimes used as a distinctive building material.

Designed parklands and gardens make a dramatic contribution to the area, with prominent follies and grand houses. Other distinctive attributes include tree avenues and gatehouses. A number are the work of famous 18th-century designers such as Bridgeman, Brown and Repton.

Major roads and railway lines follow the valleys, linking London and the Midlands. Settlements along main routes have expanded considerably. Major urban centres are found near motorways at Luton and High Wycombe. There is also an airport near Luton. Business and industrial parks (often occupying former mills) lie adjacent to watercourses.

Ancient, often sunken lanes can be found beyond the network of major routes. Some run straight along valley bottoms or ridgetops and others wind up the scarp or valley sides. Away from main settlements, roads and railways, areas retain high levels of tranquillity. Concentrations of well-preserved prehistoric monuments contribute a sense of time depth. These include bronze-age burial mounds and iron-age hill forts and dykes.

A considerable number of golf courses, horse paddocks and managed public green spaces are found near settlements. Numerous parklands and woodlands are open to the public. These supplement the opportunities for access provided by commons and downland. The Thames Path and the Ridgeway National Trails pass through the area. Boating is popular on the River Thames, and the extensive rights of way network supports horse riding, walking and cycling. This includes locally promoted routes such as the Grand Union Canal, the Chilterns Cycleway and the Icknield Way Riders’ Route. Busy ‘honeypot’ sites result from easy access, with prominent visitor facilities.

The countryside has a quiet and prosperous farming and estate character. The scenic qualities of areas furthest from London are recognised by AONB designations.

The landscape through time

The NCA is defined by a Chalk outcrop that formed between 95 and 70 million years ago. Deposits on a bed of warm, shallow, lime-rich seas built up over Upper Greensand and Gault Clay. This created distinct bands of chalk recording changing conditions. They contain marine fossils, including ammonites. Massive earth movements 60 to 40 million years ago tilted the landscape to form the London Basin. High on the northern rim of the Basin, the Chilterns were exposed to erosion. This caused a reduction in the height and westward extent of the Chalk. During the Quaternary, ice sheets overrode the outcrop in the north. This lowered the escarpment and blocked the passage of the Thames through the Vale of St Albans. Forced southwards, the Thames carved its gorge through the Goring Gap and shaped its gravel deposits into terraces. Upon the frozen ground of the dip slope, water could not percolate into the Chalk. It therefore carved branching valleys down into the London Basin, eroding as deep as the Melbourn Rock. Various Quaternary deposits were laid down on the Chalk, the most extensive being clay- with-flint deposits. These were created through disintegration of upper chalk bedrock by freeze-thaw action.

Quaternary deposits are associated with the earliest humans in the Chilterns. Extensive flint-working sites are found at Caddington. The largest Palaeolithic hand axe in Britain (and probably Europe) has been dated to the early Palaeolithic. Finds of Mesolithic flint implements are widespread.

Monuments, boundaries and tracks remain visible today as evidence of prehistoric people in the Chilterns. The oldest monuments, for example the long barrow overlooking Princes Risborough, date from the Neolithic. The Bronze Age is largely represented by burial mounds. Iron Age monuments consist of simple hill forts, such as Pulpit Hill, and dykes (earth boundaries), including Grim’s Dyke. There is a notable concentration of Iron Age defensive features commanding prominent hills. These overlook key routes such as the Thames, the Ridgeway and the Icknield Way.

Woodland management defines much of this landscape. Farming began in the Neolithic when woods were cleared along the scarp and river valleys. Favourable farmland in the valleys and along the springline attracted late Iron Age settlers. Existing farmsteads were later adapted into Roman villas. Thriving Roman markets, such as Verulamium (now St Albans), and a growing population encouraged farmers onto marginal soils. This is evidenced by the remains of Roman farmsteads and fields; many now preserved under woodland. Verulamium was connected to London by Watling Street through the Ver Valley (now the modern A5). To the west it was connected by Akeman Street following the Bulbourne Valley (now the A41). Charcoal produced from the woodlands was an important resource for the Roman iron smelting industry.

The marginal agricultural land of the plateau lent itself to woodland and rough grazing. Minor droveways developed, linking the vales to the plateau. Saxon estate boundaries indicate the equal apportionment and distribution of resources of clay vale, springline, chalk escarpment and wooded plateau. The marginal growing conditions on the plateau made farming sensitive to phases of reclamation and abandonment. Population declines and a collapse in agricultural markets in the 5th and 6th centuries led to abandonment. By the time of Domesday in 1085-86, woodland had spread to exceed today’s cover.

‘Manorial wastes’ were established between the 10th and 13th centuries across the plateau, often linked by thin tracts of land. Commons provided small centres for industry, producing bricks, tiles and lime. They were also used for occasional grazing, firewood and as places for local gatherings.

The 12th century saw another period of population growth and ‘land hunger’. This drove renewed woodland clearance and the establishment of farms and settlement. Some steeper slopes were cultivated for the first time. Medieval assarts and strip lynchets provide evidence of intense agricultural activity during this period. Monasteries, such as Missenden Abbey, were also accumulating land into large estates and establishing priories. Clearance of common woods slowed towards the end of the 13th century.

The value of woodland produce and the low fertility of some areas ensured the retention of substantial areas of woodland. In the 13th century, demand from the adjacent vales for timber and firewood also stemmed the steady clearance. Many wooded commons were enclosed as private property, and further woodland was enclosed in parks.

Tudor population increases instigated resurgence in clearance for agriculture. This included enclosing common heaths. Woodlands in the south were saved from clearance by London’s demand for firewood and timber. The proximity to the Thames shipping route also ensured their survival.

Since 1600, approximately 12,000 ha have remained under continuous woodland cover. The 18th and 19th centuries saw demand from the local furniture industry for beech timber. This grew from its ‘cottage industry’ beginnings to a nationally recognised, large-scale industry known for the ‘Windsor’ chair. This industry drove widespread planting of beech and the conversion of many semi-natural mixed woods into beech. Coppice for charcoal was devalued by the opening of the Grand Union Canal, which made coal more readily available. Secondary woodland cover also increased. Ancient woodlands were extended, particularly in Oxfordshire. The agricultural depression of 1880 to 1940 led to the scrubbing up of downland and commons, including Totternhoe and Naphill.

Further change in the 18th and 19th centuries was associated with agricultural improvements. This involved the Parliamentary enclosure of commons and the re-organisation of farm and older boundaries. Some commons were lost entirely, including Wycombe, while others, such as Berkhamsted, survived intact. The Chilterns also became a focus for the wealthy, who established grand houses and fashionable parks and gardens. Many had earlier antecedents as hunting parks but were substantially remodelled or expanded. Designed landscapes include examples by Lancelot ‘Capability’ Brown and Humphry Repton. Many large estates survive, having diversified to include schools, tourist attractions and shooting estates.

Water-powered mills, which first appeared during medieval times, gradually increased in number. It was not until the 19th century that the paper industry reached an industrial scale along the Wye and Gade. At a similar time the Chilterns became famous for apples and soft fruit. Orchards survive today, particularly around the ‘cherry pie villages’ of Seer Green and Holmer Green.

The 19th century saw the first deliberate construction of transport networks since Roman times. Turnpike trusts improved all the main routes running along the through-valleys. The Grand Union Canal, railways (including three London mainlines) and motorways followed. The effect of improved connections with the capital was dramatic, leading to development of light industry and suburbs. This is most clearly seen in the ‘Metroland’ suburbs along the Metropolitan Line, which were promoted as accessible rural retreats. With suburbanisation came an increase in recreational land use, with areas of downland converted to golf courses.

Many towns and villages have retained their historic core, with notable medieval buildings and Norman churches. However, many have expanded substantially. Settlements on the plateau have more recent origins in the 19th century. Luton was an early ‘new town’ and remains a focus for growth. Old mill sites along chalk streams have been redeveloped as business and industrial estates. Three industrial-scale cement works extracted material from the scarp in the 20th century but have subsequently closed.

In the countryside there has also been recent change. Post-war hedgerow removal saw the creation of some prairie fields, particularly concentrated in Hertfordshire and Bedfordshire. The continuing decline of livestock farming led to further significant areas of open land being lost to scrub and woodland. Traditional grazing and clearance of scrub became a conservation activity. The woodland resource also fell out of management with the demise of the local furniture industry. However, increasing local demand for wood fuel in recent years has incentivised management in some woods. Farms have evolved to include increasing numbers of ‘hobby’ farms and historic farm buildings converted to dwellings and offices. In the face of change, the countryside furthest from London has been conserved by AONB designations. The Chilterns AONB to the north of the Thames was designated in 1965. To the south of the Thames, the North Wessex Downs AONB was designated in 1972.