The Chiltern Hills run diagonally across southern Buckinghamshire from south-west to north-east, an escarpment of chalk topped with beech woods that turn copper in October. The highest point, Haddington Hill in Wendover Woods, reaches just 267 metres - a Chiltern summit is a different scale of mountain than a Lakeland one - but the ridge has functioned for centuries as a barrier between the Thames Valley and the Vale of Aylesbury. The Romans called the inhabitants Catuvellauni, the road-makers cut the Icknield Way across the foot of the scarp, and the Anglo-Saxons settled in the wooded coombes. Today the Chilterns are an Area of Outstanding Natural Beauty. Walkers come for the long-distance Ridgeway path, which runs along the chalk crest of southern England, and for the red kites that were reintroduced here in 1989 and now drift over every village in numbers the early conservationists never dared to hope for.

In a small parish churchyard on the edge of the village of Stoke Poges, in the south of the county, Thomas Gray wrote the lines that became one of the most famous poems in the English language. 'Elegy Written in a Country Churchyard,' completed in 1750, made Gray instantly famous and gave English literature its enduring image of pastoral melancholy. The yew tree he sat under is still there. So is the church, with its medieval brickwork and the gravestones he watched at twilight. The churchyard has been kept almost unchanged for two and a half centuries - a working parish church, not a museum, but visitors come anyway and read the lines on the memorial in the field next door. 'The curfew tolls the knell of parting day.' He meant the curfew bell of this exact village.

Great Missenden, a Chiltern village halfway between Amersham and Wendover, was Roald Dahl's home for the last thirty-six years of his life. He lived in a white-painted Georgian house called Gipsy House, and he wrote in a small brick garden hut about ten metres from the back door. Inside the hut was a high-backed wing chair, a sleeping bag for his legs, a desk on his lap with a wooden plank balanced on the arms, and a yellow Dixon Ticonderoga pencil. Charlie and the Chocolate Factory, James and the Giant Peach, The BFG, Matilda - all came out of that hut. After Dahl's death in 1990 the hut was preserved exactly as he left it; in 2011 the entire interior was transferred, brick by brick, into the Roald Dahl Museum and Story Centre in the village. The house remains private. The hut you can visit. The pencil sharpener is still on the windowsill.

In a rambling Victorian mansion in the north of the county, near the railway junction at Bletchley, a quiet revolution happened between 1939 and 1945 that probably shortened the Second World War by two years. Government Code and Cypher School - the codebreakers - moved to Bletchley Park because it sat on the main line between Oxford and Cambridge, where the mathematicians were. Alan Turing and Gordon Welchman designed the Bombe machines that broke the German Enigma cipher. Tommy Flowers and Bill Tutte built Colossus, the world's first programmable electronic computer, to break the higher-grade Lorenz cipher used between Berlin and field commanders. At its wartime peak, nearly ten thousand people worked at Bletchley, sworn to absolute secrecy. None of them spoke about what they had done until the 1970s. The site is now a museum. Walking past the wooden huts, between flower beds, you find yourself standing where modern computing began.

The Rothschild banking family bought up much of the Vale of Aylesbury in the nineteenth century - so much of it that locals called the area 'Rothschildshire.' Waddesdon Manor, built between 1874 and 1889 by Baron Ferdinand de Rothschild in the style of a French chateau, sits on a hilltop above the village of Waddesdon, looking utterly out of place and somehow entirely settled. It now belongs to the National Trust but is still run by the Rothschild family. Mentmore, Halton, Tring, Aston Clinton, Ascott - five great Rothschild houses, all within a few miles of one another, all built in a generation and a half. The family was changing England. The county has other layers too: Stowe House and Stowe Gardens north of Buckingham, with their eighteenth-century landscape designed by Capability Brown; Cliveden above the Thames, where the 1963 Profumo scandal began at a swimming pool party; Hughenden, where Benjamin Disraeli lived as Prime Minister. The houses are why people come. The villages between them are why they stay.