Roy Jenkins was probably the best Prime Minister Britain never had. But though he never reached 10 Downing Street, he left a more enduring mark on British society than most of those who did. His career spans the full half-century from Attlee to Tony Blair during which he helped transform almost every area of national life and politics.

First, as a radical Home Secretary in the 1960s he drove through the decriminalisation of homosexuality and the legalisation of abortion, abolished theatre censorship and introduced the first legislation to outlaw discrimination on grounds of both race and gender. Second, he was an early and consistent advocate of European unity who played a decisive role in achieving British membership first of the Common Market and then of the European Union.

Third, in 1981, when both the Conservative and Labour parties had moved sharply to the right and left respectively, he founded the centrist Social Democratic Party (SDP) which may have failed in its immediate ambition of breaking the mould of British politics but merged with the Liberals to form the Liberal Democrats and paved the way for Tony Blair’s creation of New Labour.

On top of all this, Jenkins was a compulsive writer whose twenty-three books included best-selling biographies of Asquith, Gladstone and Churchill. He knew and cultivated everyone who mattered in the overlapping worlds of politics, literature, diplomacy and academia; he also had many close women friends and enjoyed an unconventional private life. His biography is the story of an exceptionally well-filled and well-rounded life.