(Read more at Hillsdale College Churchill Project)
Churchill’s faith in personal diplomacy—solving intractable problems by meetings at the highest level—was famously expressed during World War II.
Less widely known is Churchill’s 1914 proposal for a conference of heads of state (including, it seems, French President Raymond Poincaré) in an effort to head-off World War I. The scheme failed, but not for Churchill’s lack of trying.
There is little on Churchill’s “kingly conference” in the literature. There is no reference in Churchill’s The World Crisis, Asquith’s memoirs, or biographies by Manchester, Jenkins, Rose, Charmley and Birkenhead, though Sir Martin Gilbert includes in the official biography an excerpt from a cabinet member which records Churchill’s words in the cabinet of July 27th:
Churchill said we were now in a better than average condition, & the fleet was at war strength….Churchill, however, added: it was an appalling calamity for civilised nations to contemplate & thought possibly sovereigns could be brought together for sake of Peace. 
Although there is evidence that the principal powers were willing to participate, Churchill’s proposal was dashed. On July 28th he wrote his wife Clementine from the Admiralty, expressing his continued wish for peace:
I cannot feel that we in this island are in any serious degree responsible for the wave of madness which has swept the mind of Christendom. No one can measure the consequences. I wondered whether those stupid Kings and Emperors could not assemble together and revivify kingship by saving the nations from hell but we all drift on in a kind of dull cataleptic trance. As if it was somebody else’s operation! 
1. Martin Gilbert, ed., Winston S. Churchill, volume 3, The Challenge of War, 1914-1916 (Hillsdale, Michigan: Hillsdale College Press, 1971), 10.
2. WSC to his wife (CSC Papers), Tuesday, 28 July 1914, in Randolph S. Churchill, ed., Winston S. Churchill, Document Volume 5, At the Admiralty 1911-1914 (Hillsdale, Mich.: Hillsdale College Press, 2007), 1989-90.