The Russia House (1990) on Netflix

Three notebooks supposedly containing Russian military secrets are handed to a British publisher during a Russian book conference. The British secret service are naturally keen to learn if these notebooks are the genuine article. To this end, they enlist the help of the scruffy British publisher Barley Blair, who has plenty of experience with Russia and Russians. Barley, an unconventional character who doesn't respond well to authority, finds himself in a game more complex than he first thought when he digs into the origin of the notebooks.