 He was then on the staff of the "Daily Mail" from 1971 to 2003, where he was initially deputy to Paul Callan, but replaced him as the newspaper's diarist in 1973.While Dempster was sometimes inaccurate, for instance dismissing suggestions that Prince Charles would marry Lady Diana Spencer, he forecast in 1975 that Harold Wilson would soon resign as Prime Minister, three months before he did so in 1976.Supposedly this took everyone by surprise, but a contact of Dempster's had overheard the Foreign Secretary James Callaghan discussing it.