Twice elected British Prime Minister and WWII hero (1874-1965). In 1937 Churchill was to embark on an ambitious project, to write a book on the history of Britain and its former colonies across the world. Finally completed in 1957, the result was four volumes collectively titled 'A History of the English Speaking Peoples'. We have a typed 'Supplemental Agreement' to an existing book contract for amending the agreement, on parchment, covering one and one fifth of the folded document signed 'Winston L.S. Churchill', noted 'London, January 18th, 1957'. Churchill's signature is penned at the conclusion, partially covering the seal, and is witnessed by a solicitor. Bears embossed revenue stamp at head. Exceptionally fine condition. An extremely rare agreement between Churchill and his publisher covering one of his most important works.