He had a "well-known belief that Hitler was essentially a good man who wanted only to build a new and better Germany." Opposed to war and believing that wars were caused by Jewish "usurial moneyed interests", he was attracted to Oswald Mosley's British Union of Fascists and joined it in 1937. Mosley became Hereward Birkin in Williamson's "Chronicle of Ancient Sunlight" (possibly a reference to Hereward the Wake and Freda May Birkin). On the day of the British declaration of war, Williamson suggested to friends that he might fly to Germany to speak with Hitler to persuade him away from war. Following a meeting with Mosley later that day, however, he was dissuaded from his plan. At the start of the Second World War, Williamson was briefly held under Defence Regulation 18B for his political views, but he was released after only a weekend in police custody. Visiting London in January 1944, he observed with satisfaction that the ugliness and immorality represented by its financial and banking sector had been "relieved a little by a catharsis of high explosive" and somewhat "purified by fire". In "The Gale of the World", the last book of his "Chronicle", published in 1969, Williamson has his main character Phillip Maddison question the moral and legal validity of the Nuremberg Trials. This book also hinted at a plot to rescue Rudolf Hess from Spandau prison. Williamson initially retained a close relationship with Mosley in the immediate aftermath of the war, but when he brought Mosley as his guest to the Savage Club, the former BUF leader was asked to leave. Williamson refused Mosley's request to join the newly established Union Movement and indeed, his suggestion to Mosley that he should instead join him in abandoning politics altogether led to the two men falling out. Nonetheless, Williamson would write for the Mosleys' theoretical journal "The European". He also continued to express admiration for aspects of Nazi Germany after the war. After the war the family left the farm. In 1946 Williamson went to live alone at Ox's Cross, Georgeham in North Devon, where he built a small house in which to write. In 1947 Henry and Loetitia divorced. Williamson fell in love with a young teacher, Christine Duffield, and they were married in 1949. He began to write his series of fifteen novels collectively known as "A Chronicle of Ancient Sunlight". In 1950, the year his only child by this marriage Harry Williamson was born, he edited a collection of poems and short stories by James Farrar, a promising young poet who had died, at the age of 20, in the Second World War.