The life of Bertrand Russell, born when Queen Victoria had nearly three decades still to reign, was one of the most influential of the twentieth century, as well as one of the most controversial. He resolved to write two series of books 'in the philosophy of the sciences and 'on social and political questions ; and for the next three quarters of a century he switched from one to the other in an astonishing range of publications which gave him a position unique among other Englishmen of his time. But the Bertrand Russell of A History of Western Philosophy, the man who put an 'absolute unbridled Titanic passion' into Principia Mathematica, was also a controversial figure on the world stage.

He served two prison sentences: the first during the 1914-18 war for making 'statements likely to prejudice His Majesty's relations with the United States of America', the second in 1961, in his 90th year, for inciting the public to civil disobedience. Russell's personal life was as turbulent as his public activities. With the most famous of his mistresses, Lady Ottoline Morrell, he found a 'kind of restfulness and sense of home-coming in her 'aristocratic habits of mind', but he also married no fewer than four times.

Ronald Clark was born in London in 1916 and educated at King's College School. In 1933 he chose journalism as a career; during the Second World War, after being turned down for military duty on medical grounds, he served as a war correspondent. During this time Clark landed on Juno Beach with the Canadians on D-Day and followed the war until its end, then remained in Germany to report on the major War Crimes trials.

Clark returned to Britain in 1948 and wrote extensively on subjects ranging from mountain climbing to the atomic bomb, Balmoral Castle to world explorers. He also wrote a number of biographies on a myriad of figures, such as Charles Darwin, Thomas Edison, Albert Einstein, Benjamin Franklin, Sigmund Freud, and Bertrand Russell. Clark died in 1987.