IF EVER A life demanded two volumes of biography, it is W B Yeats's. He lived, at the very least, two long lives - as poet and as public man - and owed allegiance to two countries. In old age he told his friend Oliver St John Gogarty, 'the best life consists of six weeks in England and six weeks in Ireland alternately'.

Roy Foster's long-awaited Vol II has arrived - as magisterial, graceful and encyclopedic as one would expect of Oxford's Carroll Professor of Irish History, successor to the late Leland Lyons who took on the task forty years ago. Foster has devoted fifteen years to getting this prodigious life between four