Buckinghamshire , abbreviated Bucks, is a county in South East England which borders Greater London to the south east, Berkshire to the south, Oxfordshire to the west, Northamptonshire to the north, Bedfordshire to the north east and Hertfordshire to the east. Buckinghamshire is a home county and towns such as High Wycombe, Amersham, Chesham and the Chalfonts in the east and southeast of the county are parts of the London commuter belt, forming some of the most densely-populated parts of the county. Development in this region is restricted by the Metropolitan Green Belt. Other large settlements include the county town of Aylesbury, Marlow in the south near the Thames and Princes Risborough in the west near Oxford. Some areas without direct rail links to London, such as around the old county town of Buckingham and near Olney in the northeast, are much less populous. The largest town is Milton Keynes in the northeast, which with the surrounding area is administered as a unitary authority separately to the rest of Buckinghamshire. The remainder of the county is administered by Buckinghamshire County Council as a non-metropolitan county, and four district councils. In national elections, Buckinghamshire is considered a reliable supporter of the Conservative Party. A large part of the Chiltern Hills, an Area of Outstanding Natural Beauty, runs through the south of the county and attracts many walkers and cyclists from London. In this area older buildings are often made from local flint and red brick. Many parts of the county are quite affluent and like many areas around London this has led to problems with housing costs: several reports have identified the market town of Beaconsfield as having among the highest property prices outside London. Chequers, a mansion estate owned by the government, is the country retreat of the incumbent Prime Minister. To the north of the county lies rolling countryside in the Vale of Aylesbury and around the Great Ouse. The Thames forms part of the county’s southwestern boundary. Notable service amenities in the county are Pinewood Film Studios, Dorney rowing lake and part of Silverstone race track on the Northamptonshire border. Many national companies have offices in Milton Keynes. Heavy industry and quarrying is limited, with agriculture predominating after service industries.