In one of the opening scenes of the city is a theater marquee showing Phyllis Calvert and Marius Goring in Ronald Duncan's play Ménage à Trois. In 1963, when this episode was filmed, the theater would have been the Lyric Theater, located on Shaftesbury Avenue in the City of Westminster. The Lyric opened there in 1888.
TV and film debut of Ingrid Pitt.
Also in the opening scene at the start,notice the play Boeing Boeing this play later a film starring Tony Curtis,who starred with Roger Moore in the Persuaders.
The introductory location shot of the Lyric Theatre on Shaftesbury Avenue, London, UK must have been taken between 12 March and 6 April, 1963. That is the period during which the production, Menage a Trois, ran at the Lyric. In fact, 12 March was within a week of the last day of the record cold winter of 1962/63.
Phone in Paris bar standard contemporary UK GPO issue.