Molly Goddard is perhaps the first designer in fashion history to find fame by dressing a psychopath. The frothy, bubblegum-pink dress that became synonymous with the character of Villanelle, played by Jodie Comer in Killing Eve, rocketed Goddard from the ranks of promising young British design talent to become a major fashion player.

Villanelle struck again at London fashion week on Saturday. Goddard’s 10th collection, shown to a packed house in an art deco leisure centre in central London, gave the fashion crowd more of the voluminous, highlighter-bright dresses which Goddard has made into a phenomenon, and closed with model Edie Campbell wearing a billowing taffeta fuchsia cloud-gown. This season’s Molly Goddard woman is, as always, uninhibited and overdressed. She wears smocked tulle, puffball taffeta or ribbon-gathered calico. With its jelly baby palette and off-kilter silhouette, the look is a riot of deliberately mixed messages. Think Comme des Garcons’ Japanese avant-garde chic crossed with Bonpoint’s deliciously French upscale childrenswear.

But this collection also showed how Goddard has evolved. It was less madcap, more sophisticated. A more understated customer who would never wear pink tulle will be seduced by the softly ruched coats and dresses in muted caramel and matt calico, and textured knitwear with subtle cutout detailing.

Facebook Twitter Pinterest Molly Goddard says she is not interested in ‘trendy’, only making clothes that last forever. Photograph: PR

The 30-year-old designer, winner of last year’s BFC/Vogue Designer Fashion Fund and an LVMH prize finalist in 2017, said before the show that the collection was about “looking back at things I’ve done before and really, really loved, and working out how I can do them even better. I’m not interested in trendy. I only want to make things that you will keep for ever. We worked a lot on pattern cutting, to figure out how to make as much volume as possible.” In direct contrast to traditional eveningwear construction, where boning and padding is hidden beneath the surface, Goddard’s dresses hold their own with no hidden shape. Goddard likes the “directness” of this, as well as that it makes the clothes “super comfy”.

The fashion phenomenon for oversized, frothy dresses sparked by Goddard has been dubbed big dress energy. Pink tulle dresses were a trend on the Oscars red carpet this year, from actress Gemma Chan’s Valentino to singer Kacey Musgrave’s Giambattista Valli. Having studied knitwear at Central St Martins, Goddard taught herself pattern cutting using old-fashioned baby dresses she found in her mother’s attic. “There were all these beautiful smocked baby dresses, some made by my granny and some bought in charity shops. I blew those up and made oversized patterns, taking a tiny baby dress and making it a hundred times bigger.” The distinctive shape of baby dresses, with their oversized sleeves and short, wide trunks created this new and unusual silhouette. Goddard began using the tulle which has become her signature because it is cheap and light to wear – both crucial considerations when up to 90m of fabric is used in a dress.

Facebook Twitter Pinterest Goddard began using the tulle because it is cheap and light - crucial when up to 90m of fabric is used in a dress. Photograph: PR

Villanelle is to Goddard as Audrey Hepburn was to Hubert de Givenchy, but the connection came about by accident. The script for the second episode of Killing Eve specified a “big, poufy dress”, costume designer Phoebe de Gaye told Vogue last year. “I think Phoebe Waller-Bridge … had something more classic in mind, [but] I thought Molly Goddard’s stuff was just perfect for it because it has that subversive streak.” De Gaye bought the dress directly from Goddard while the first series was still in production. “It was all very organic,” recalls Goddard. “It wasn’t until more than a year later that Killing Eve came out, so by then I’d almost forgotten they’d even bought a dress. And all I knew about the programme at that point was that it was about a glamorous murderer, or something.” When she eventually watched the show, and saw on-screen Jodie Comer standing in Place Vendôme in her pink dress and black Balenciaga biker boots, “I thought it was perfect. It worked because they totally got what that dress was about.”

On Tuesday, the dress is one of four looks from Killing Eve which will go on display at the Behind the Screens exhibition opening at Bafta.