Backstage at Vivienne Westwood’s Paris show the designer was in typically provocative mood, declaring: “I am not sure how much longer fashion weeks will be feasible for, in the future.” However, that designer was not Westwood herself but her husband, Andreas Kronthaler, who for the past three years has taken top billing at the Andreas Kronthaler for Vivienne Westwood show.

This label remains unmistakably Westwood. It retains both its distinctive look – think 18th-century French punk – and the environmental activism she embraced decades before it became acceptable, let alone fashionable, in mainstream culture. The Dame herself watched Saturday’s show from the front row, and joined Kronthaler arm-in-arm for a catwalk lap of honour.

“We have to take sustainability seriously,” said Kronthaler before the show. “I think that is obvious now, no? So I try to be as conscious and as careful as possible.” Much of the raw material for this collection was “fabrics that already exist – it’s called deadstock, although I think that’s a bit of a strange name”. He worked with Wastemark to collect fabric surplus from top Italian mills, “and mostly I didn’t dye the fabric, just washed it and fitted it”.

Bella Hadid walks the runway in swimsuit and knee-high socks. Photograph: Thierry Chesnot/Getty Images

This collection was called Rock me Amadeus. “But really, that’s just about the hair,” said Kronthaler, gesturing to model Bella Hadid, standing patiently in a swimsuit and knee-high sport socks while being accessorised for the catwalk with a vast Dr Seuss hat on top of hair neatly pinned into Mozart-esque rolls above the ears. “I try to put as much into each look as I can. I want each look to be a world of its own.”

An oversized black net hat with an elegant elongated shape, somewhere between a very chic crocodile mask and an Admiral’s bicorne hat, had in fact been inspired by rowers who Kronthaler saw carrying their upturned boats high above their heads into the Thames, on a visit to Henley. There were references to 1950s pin-ups and to Fellini’s 1976 film Casanova. And there were plenty of party dresses in the classic Westwood style, with opulent layers unpeeling over bare shoulders, waists cinched with a corset, skirts flounced.

There were plenty of party dresses in the classic Westwood style. Photograph: Thierry Chesnot/Getty Images

“What I believe is that we should buy less and really love the things that we buy,” said Kronthaler.

The son of a Tyrolean blacksmith, he met his wife in the late 1980s, when she was a professor at the Vienna Institute for Applied Art and he was her star pupil. Married since 1993, they have been a de facto design team for much of that time. In 2016, the name of the Paris fashion week show was changed to acknowledge Kronthaler’s contribution.

He said: “I have reduced the collection to its essence – if people are going to buy less, then I should be making less – and then to stretch it into a show I make some pieces with fabric that is dormant around the studio.” A box of scrapped sequins found in a cupboard became an one-off sparkly fish, worn as an enormous hat, and embellishment for a T-shirt dress with the face of a tiger, to support the work of Fauna and Flora International, the world’s first international wildlife conservation organisation, in their mission to protect the critically endangered Sumatran tiger, of which fewer than 400 are estimated to remain in the wild.