Grace has agreed to marry Sir Harcourt in return for his financial support of her family. At a house party in her father's place, Harcourt's son Charles also falls in love with Grace. When his father appears on the scene, he has to convince him that there is a case of mistaken identity and he is somebody else. Then Lady Gay Spanker, a married woman also visiting at the house, is persuaded by Charles to seduce his father and thus divert his attention from Grace. Much confusion and scheming ensues.
Unfortunately the movie National Theatre Live: London Assurance is not yet available on HBO Max.
| Writing | Dion Boucicault | Writer |
| Directing | Nicholas Hytner | Director |
| Costume & Make-Up | Beverley Binda | Makeup Department Head |
| Lighting | Neil Austin | Lighting Design |
| Sound | Rachel Portman | Music |
