Josef Stalin and Winston Churchill had an all-night drinking session in Moscow that lasted until 3am during World War II.
Relations between the Russian and British leaders were stiff until Churchill arranged a late-night banquet in August 1942 with Stalin, according to files held by Britain's National Archives.
The event was recorded by Foreign Office permanent under-secretary Sir Alexander Cadogan.
The mood was "merry as a marriage-bell," he added, though Churchill was complaining of a "slight headache" when Cadogan came to find him at 1am.
The two men did not engage in much military talk during the meeting, which went on until 3am.
The evening was dubbed a success by Cadogan, as the two men got on.
"Certainly Winston was impressed, and I think the feeling was reciprocated," he wrote in a letter.
"We broke up soon after 3(am), giving me just time to get back to the hotel, pack, and leave for the aerodrome at 4.15(am)."
The BBC reports the letter was among almost 600 government files dating from World War II and the early years of the Cold War, released by the National Archives.