When principal photography began in August 1979 the original intention was for a 15- to 16-week shoot, but it ultimately took one year. Filming took place in five different countries and at various points the crew had to wait for snow to fall in Helsinki (and other parts of Finland), which stood in for the Soviet Union, and for rain to stop in Spain. A cottage in Kent was used to depict exteriors of the Reeds' home in Croton-on-Hudson, which in reality was a small early American saltbox house. The interior sets built at Twickenham Studios were also enlarged to evoke the "flavor" of the real home without reproducing it exactly. Other English locations included Frensham Ponds in Surrey, which stood in for Provincetown, the Smeaton Room of the Institution of Civil Engineers at One Great George Street for the Liberal Club meeting room in Portland, and the interior of Lancaster House for that of the Winter Palace in St. Petersburg.