“Disgruntled debutante” was the juicy character Simone Rocha portrayed for spring, yielding a young, frisky and slyly sultry collection.

The designer had read a 1992 essay by Maureen Freely about a young girl who had to wear her mother’s clothes and “wasn’t too happy about it.”

Hence the taciturn expressions and folded arms of the models, who whisked through Mansion House to a wackadoodle-yet-mesmerizing soundtrack stretching from Doris Day ditties to witch house doom and gloom from Salem and White Ring.

They wore sparkly bra tops and gauzy hoop skirts, quilted bed jackets and plastic raincoats, much of this new territory for Rocha, here easing up on ruffles, trailing ribbons and pearl embroideries. Some models hugged leather pillows edged in broderie anglaise.

Volume around the hips has been the big story on London runways, and Rocha incorporated bustles and panniers into many dresses and skirts, often exposing the crinolines that have underpinned her darkly romantic designs since forever. Here, lighter colors and fabrics — plus bloomers and boyish briefs — imparted more of an adolescent/ingenue vibe.

In a backstage scrum, Rocha confessed that she used to wear her mother’s petticoats and hoop skirts, hoisting them up near her armpits to approximate a dress — hence her runway exploration of grown-up femininity came from a personal place.

The menswear could not be shoehorned into this narrative, however, and felt like an afterthought.

In a London season light on big names, Rocha has become a pillar of its fashion week, offering a distinct point of view that she keeps pushing into new and interesting places.

“I really wanted to look at my fundamentals and codes, and I really wanted to push and pull them,” she said backstage. “You just want to put your best foot forward, really.”