The Bliss of Mrs. Blossom

The Bliss of Mrs. Blossom is a 1968 British comedy film directed by Joseph McGrath. The screenplay by Alec Coppel and Denis Norden was adapted from a play by Coppel that was based on a short story by Josef Shaftel, who served as the film's producer.
Plot.
Robert Blossom is a brassiere manufacturer and workaholic. When his wife Harriet's sewing machine breaks, he sends his bumbling employee Ambrose Tuttle to repair it. Mrs. Blossom seduces Ambrose, then hides him in the attic, instructing him to sneak out in the middle of the night. However, Ambrose is enchanted by Harriet and decides to settle in to serve as her secret paramour. When Ambrose is reported missing, Det. Sgt. Dylan from Scotland Yard is assigned to the case, one he doggedly pursues for years. The mysterious noises Robert frequently hears overhead finally lead to his nervous breakdown, but Ambrose saves the day by passing along stock tips that turn his employer into a millionaire. The grateful Mr. Blossom not only allows Ambrose to remain with his wife, but presents the couple with his factory as a wedding present.
Story.
The film is loosely based on a real incident. In the early 1920s, Walburga Oesterreich kept her lover Otto Sanhuber in the attic where he lived for many years. The real story does not have the happy ending of the movie.
Production notes.
Joseph Shaftel said the script was based on a story of his, which in turn was based on a true story.
Shirley MacLaine was a last-minute replacement after the original star pulled out. Her fee was a reported $750,000.
Assheton Gorton served as the production designer for the film.
Location scenes were filmed in Putney, Bloomsbury, at the National Film Theatre in the South Bank Centre and at Alexandra Palace in London. Interiors were filmed at the Twickenham Film Studios in Twickenham.
The soundtrack includes the songs "The Way That I Live" performed by Jack Jones, "Let's Live for Love" by the Spectrum and "Fall in Love" by the New Vaudeville Band.
Frank Thornton, Barry Humphries Willie Rushton and John Cleese make brief appearances in the film.
Reception.
In his review in "The New York Times", Howard Thompson called the film "roguish, restrained and absurdly likable, with a neat climactic twist."
"Variety" described the film as "a silly, campy and sophisticated marital comedy, always amusing and often hilarious in impact . . . although basically a one-joke story, [the] idea is fleshed out most satisfactorily so as to take undue attention away from the premise. Performances are all very good, Attenborough's in particular."
"Time Out New York" called the film a "coarse comedy which looks a little like Joe Orton gone disastrously wrong . . . any sparks in the script or performances are ruthlessly extinguished by atrocious direction."