Robert Harris’s Precipice, reviewed: it’s an injustice this great novelist hasn’t won more literary prizes

During the dawn of the First World War, HH Asquith sent more than 700 letters to an aristocratic young woman almost half his age – but did the Liberal PM actually have an affair with Venetia Stanley? The story forms the basis of one of the most enthralling novels yet from ‘Fatherland’ author Robert Harris, writes Nicholas Coleridge