Top Secret

Christopher Lee was the agent who phone to report Potts (George Cole)

"When permission was granted at the highest level, to bring this historic and international document the screen, the producers were confronted with a major problem: namely, that from time immemorial the British have believed English to be the only language worth speaking. Foreigners should either speak it or be silent. For example, how many here present understand French or Russian? How many even know the Russian word for 'yes'? Come to that, how many Russians know it? It was decided, therefore, that regardless of nationality, the characters in this film should, in the main, speak English. We draw attention to this in order to reassure anyone who might gain impression (false, alas!), that English has at last become the official language of France and Russia."

References The Third Man (1949)