Top Secret aka [US] Mr.Potts Goes to Moscow UK1952

George Potts, a plumber in a top secret government research plant, accidentally comes into possession of the plans for a revolutionary atomic weapon. As George leaves for his annual holiday, the research security team embarks on a nationwide search for the hapless 'sanitary engineer.' Meanwhile, the Russians get wind of the incident and intercept George, plying him with liquor and employment promises so that he'll hand over the plans to them. Starring: George Cole, Oskar Homolka, Nadia Gray