ABOUT 100 kilometers southeast of London, in the middle of the rolling hills of West Sussex, lies a stately 16th century manor house, surrounded by more than 3,000 hectares of parkland. It could easily be one among hundreds of historical buildings dotting the British landscape that tourists seek out when they visit the United Kingdom. But since 1951, Wiston House has been home to the Wilton Park conferences, one of the world’s leading venues