"Do you think I would cheat?" asks fun-loving ingenue Gigi as she plays cards with bored Parisian playboy Gaston (Thomas Borchert). "You're a woman," he answers.
"Women!" declares Gaston's uncle, Honoré. "The last invention of God after an exhausting week."
"Nature only provides us with the raw materials," declares Gigi's aunt Alicia, checking her figure-hugging bodice while coaching her innocent niece on a courtesan's mercenary tactics.
You would have to be po-faced and too PC to be offended, but old-school attitudes are just not as funny when they are written to be laughed with instead of laughed at.
And unlike Lerner and Loewe's smash My Fair Lady, the sexism is not here to highlight social injustice, it is just here.
Even an in-form Topol can't divest Thank Heavens For Little Girls of the dodginess with which the lecherous Maurice Chevalier endowed the song in the 1958 movie.
As if sensing that, director Tim Sheader has his cast join Topol in the chorus, and any suggestion of underage sexual exploitation evaporates into Regent's Park's cleansing air.
Topol will find a more natural speech rhythm as the run progresses. But at the moment it is as if he is checking Lerner's words are in the right order before they leave his mouth.
Still, when he sings, especially the witty I Remember It Well with Millicent Martin's Mamita, his voice is warm and sonorous and there are even shades of sweet Tevye, the role that made him an international star.
And by the time Linda Thornson's Aunt Alicia reveals a courtesan's cynicism in a surprisingly edgy scene that anticipates the modern pre-nup, Sheader's excellent production, led by a Lisa O'Hare's likable and - for Gaston - lovable Gigi, has won the day.