I remember a fragment of a TV documentary years ago, about archaeological excavations of a fort that was part of Hadrian"s Wall. Amazingly, a bundle of letters written on bark had been found and, after laborious, careful conservation, had been read. They were from a centurion to his wife. Possibly, when the posting came through, the wife sorted out her belongings, dumped what she couldn"t carry on a bonfire, and the...