LONDON, Sept 13, 2024 (BSS/AFP) - A hotly anticipated party thrown by high-street retailer H&M with pop star of the summer Charli XCX shook things up with an unusual opening night of London Fashion Week on Thursday.

The LFW Spring/Summer 2025 schedule, which runs until Tuesday, had been set for weeks when H&M burst onto the scene announcing a collaboration with the British singer, overshadowing big-name designers and being labelled the hottest fashion week ticket.

Multiple screens in a sports arena in east London flashed videos of H&M's new collection, followed by a rave-like dance performance showing the pieces in action.

Sleek leather jackets and minimalist knitwear captivated hundreds of attendees in a unique take on a fashion show, as the Swedish fast-fashion giant looks to present itself as a more upmarket brand.

Moments later, Charli XCX burst on a stage to perform an explosive set from her latest hyper-pop album, "Brat", against a backdrop of its green album logo.

The past few months have been termed "brat girl summer", with the album namechecked everywhere from social media to politics -- and now fashion.

The trend emphasises an aesthetic and lifestyle inspired by Charli's club album that offers a heavy dose of party-girl energy with undertones of youthful anxiety.

The collaboration is "exciting", said Caroline Rush, chief executive of the British Fashion Council (BFC).

The BFC is celebrating London Fashion Week's 40th anniversary and vying to remain relevant to younger audiences after an exodus of designers over the past two decades.

- 'Pre-loved' -

Ahead of the H&M party, the fashion week frenzy kicked off Thursday in a contrasting vein with two shows featuring second-hand clothing to encourage sustainability in the fashion industry -- one of the world's biggest polluters.

Online auction platform eBay put on its "Endless Runway" catwalk with "pre-loved" designer clothes that were sold on the second-hand website's live shopping platform at the same time as the show.

And the Oxfam charity returned with its "Style for Change" runway, partnering for the first time with second-hand online marketplace Vinted for a buzzing catwalk featuring clothes picked out by designer Bay Garnett from Oxfam warehouses.

The catwalk aimed to showcase the "joy and innovation of second-hand fashion" and "break the stigma that still might be associated" with it, a Vinted spokesperson said ahead of the show.

Featuring models donning clashing patterns, velvet dresses, different takes on workwear and period dresses, the catwalk had something for everyone. Some of the clothes will be available to buy on Vinted after the show.

British fashion designer Katharine Hamnett, known for her political slogan t-shirts, closed the show with a T-shirt reading "No more fashion victims" -- 40 years after presenting a catwalk at the first London Fashion Week in 1984.

Fashion's contribution to global emissions and waste has been in the spotlight with a report by the nonprofit group Collective Fashion Justice released ahead of fashion week finding that less than four percent of BFC members have published emission reduction targets.

Brands like H&M, Shein and Zara have come under fire for their fast-fashion practices -- cheaply mass-producing clothes to keep up with fast-changing trends, often at the cost of environmental and labour protections.

Ahead of H&M's LFW party, the retailer removed all its previous posts on Instagram before sharing a picture of Charli XCX in a leopard-print coat from its new collection.

One social media user commented on the post comparing the marketing strategy to fast fashion: "get rid of everything you had to buy the new collection".

H&M says it uses recycled materials among other initiatives to reduce its impact on the climate.

After a night of sustainable runways and high-energy music performances, the coming week will see over 70 designers present collections, from mainstays such as JW Anderson, Erdem, Paul Costelloe and Burberry to newer designers like Bora Aksu and Di Petsa.