“Mr. Imperium” (UK title: “You Belong to My Heart”) is a 1951 romantic musical drama Technicolor film made by Metro-Goldwyn-Mayer, starring Lana Turner and singer Ezio Pinza. It was directed by Don Hartman who co-wrote the screenplay with Edwin H. Knopf, based on a play by Edwin H. Knopf. The music score is by Bronisław Kaper.
Lana Turner’s singing voice was dubbed by Trudy Erwin.
In Italy in 1939, a European man calling himself Mr. Imperium (Ezio Pinza) uses a ruse to meet an attractive American woman, Frederica Brown (Lana Turner). He eventually is revealed to be Prince Alexis, an heir to the throne and a widower with a six-year-old son. He nicknames her “Fredda”, so she calls him “Al”.
When his father becomes gravely ill, he must rush to be with him, but asks prime minister Bernand (Cedric Hardwicke) to deliver to Fredda a note of explanation. Bernand instead tells her the prince is gone for good, that this is his usual method of seducing and abandoning women.
Twelve years go by. One day in Paris, a cinema’s marquee makes it clear that “Fredda Barlo” is now a movie star.
Fredda’s former love travels to California, where film producer Paul Hunter (Barry Sullivan) is now in love with her and proposing marriage.
Fredda decides to drive to Palm Springs to think about his proposal, as well as to decide which actor should co-star in her next film, about a girl who falls in love with a king.
Mr. Imperium takes a room next to hers, and soon they meet and embrace. He explains the crisis that took place at home during the war and prevented him from looking for her.
Now he wants a new life, and Fredda believes he could even portray a king in her film.
Bernand turns up, however, to say that his son is preparing to ascend to the throne.
Mr. Imperium realizes he is needed there, so he must say goodbye to the woman he loves once more.

Lana Turner plays Fredda Barlo.

Photoplay: “Despite the grandeur that sweeps from Mediteranean shores to Palm Springs gardens, the story itself never jells. Lana Turner, who is seldom given material worthy of her, looks beautiful and does more than her share to tote this bale of nonsense. Pinza is just another middle-aged actor trying to prove himself, so far as this film is concerned. Certainly his magnificent voice is woefully neglected, the few songs given him far below his vocal ability.”

Lana never was positive about this film. Saying that she used to come home sick to her stomach, because Pinza adored his cheese pastries and gallons of espresso. The public must have found it hard to take as well, because it was a box-office dud.
The only plus for Lana was that she met young Debbie Reynolds during filming and they became friends. 

Trailer:

You can watch the film here:

Lana Turner did a lot of movies. She really loved being a moviestar.
Here are the most important films in which she starred. Just click the links for more info, photos and videos.

20 April 1937: A Star Is Born
9 Oct. 1937: They Won’t Forget
24 Oct. 1937: The Great Garrick
1 Jan. 1938: The Adventures of Marco Polo
22 July 1938: Love Finds Andy Hardy
12 Aug. 1938: Rich Man, Poor Girl
9 Dec. 1938: Dramatic School
28 April 1939: Calling Dr. Kildare
18 Aug. 1939: These Glamour Girls
29 Sept. 1939: Dancing Co-Ed
19 April 1940: Two Girls on Broadway
19 July 1940: We Who Are Young
25 April 1941: Ziegfeld Girl
12 Aug. 1941: Dr. Jekyll and Mr. Hyde
2 Oct. 1941: Honky Tonk
18 Febr. 1942: Johnny Eager
27 Aug. 1942: Somewhere I’ll Find You
1 April 1943: Slightly Dangerous
19 Aug. 1943: Du Barry Was A Lady
13 Nov. 1943: The Youngest Profession
23 Aug. 1944: Marriage Is a Private Affair
8 March 1945: Keep Your Powder Dry
1 Oct. 1945: Week-End At The Waldorf
2 May 1946: The Postman Always Rings Twice
5 Nov. 1947 : Green Dolphin Street
1 Nov. 1947: Cass Timberlane
29 April 1948: Homecoming
20 Oct. 1948: The Three Musketeers
1 Sept. 1950: A Life Of Her Own
2 March 1951: Mr. Imperium
5 Sept. 1952: The Merry Widow
25 Dec. 1952: The Bad And The Beautiful
25 Aug. 1953: Latin Lovers
1 May 1954: Flame And The Flesh
7 Sept. 1954: Betrayed
13 May 1955: The Prodigal
4 June 1955: Sea Chase
14 Dec. 1955: The Rains Of Ranchipur
12 Jan. 1956: Diane
13 Dec. 1957: Peyton Place
30 Jan. 1958: The Lady Takes A Flyer
2 May 1958: Another Time, Another Place
30 April 1959: Imitation Of Life
23 June 1960: Portrait In Black
19 July 1961: By Love Possessed
2 Nov. 1961: Bachelor In Paradise
25 Dec. 1962: Who’s Got The Action?
24 Febr. 1965: Love Has Many Faces
27 April 1966: Madame X
30 April 1969: The Big Cube
7 Nov. 1974: Persecution
27 Oct. 1976: Bittersweet Love
31 Oct. 1980: Witches Brew
21 May 1982: Dead Men Don’t Wear Plaid

Sources: Wikipedia, IMDB, Rotten Tomatoes, Lana’s biography “Lana, the Lady, The Legend, The Truth“, “The Films Of Lana Turner” by Lou Valentino and “Lana Turner, The Memories, The Myths and The Movies” by Cheryl Crane.