Book excerpt: Above London. Visitors to England who marvel at this lush land on their first incoming flight now have a volume to treasure forever. Here are the famed gardens, the majestic estates, the granduer of centuries of architecture. Along with Robert Cameron's areial photographs Alistair Cooke's text is brimming with the raconteur's characteristic wit and insight. The pictorial essay begins at the Thames and follows the history of the beloved city well into the countryside.