The starlet, then 28, wrote herself instructions for getting into character as the come-hither neighbour in Billy Wilder’s 1955 rom-com.

The 113-page document, marked “FINAL”, includes pencilled notes to be “free, direct, open, honest, frank, charming – fresh, a twinkle”.

Another take demands: “My body into his as if I want to sleep with him right then & there. Swing hips again.”

The movie, which includes the scene where her dress gusts up over a vent, paired her with stage actor Tom Ewell as the lusty neighbour.

The script sells tomorrow in Dallas, Texas. Heritage Auctions said: “She prepared to play Marilyn, playing the character.”