Cousin of British Prime Minister Performs Mess Duty at U.S. Marine Base -- Private Winston Churchill Guest, second cousin of the Prime Minister of Great Britain, peels onions outside a mess hall at a U.S. Marine Corps training base in the Southern U.S. Pvt. Guest recently was commissioned a second lieutenant in the Marine Corps Reserve. For several years before the war, he was an outstanding member of the all American polo team. June 28, 1944.