Rihanna puts her clothes on: Star launches River Island collaboration, timed for London Fashion Week

Given superstar Rihanna's habit of not wearing much in the way of clothing, she might not seem the most obvious fashion designer.

But the singer unveiled her collaboration with high street chain River Island last night, in a show timed to coincide with London Fashion Week.

Zesty silk dresses tied at the waist, grey marl jersey, crop tops, and denim-on-denim made up a wardrobe that was urban and casual in its look, and which mixed high and low references in an homage to its creator's own style. Tie-dye silk and hoods made utilitarian pieces that bit more street, while a Lurex-jersey-mix gown had a disco feel. If you want to dress like Rihanna, this is what to buy – but be warned, steel abs don't come as standard.

There are those who say celebrity fashion projects – such as Topshop and Kate Moss, or Madonna for H&M – are on the wane, and that shoppers are more interested in accessible collaborations with high-end labels, but Rihanna's cool credentials will no doubt appeal to River Island's young, trend-aware customers.

Elsewhere yesterday, the second day of London Fashion Week was nothing if not eclectic.

Established names vied with fledgling talent in a crammed schedule. One of the UK's most well-known designers, Julien Macdonald's ready-to-wear collection was pitched at a glitzy client base, entitled "Viva Las Vegas" and made up of show-stopping, skin-tight and sheer minidresses encrusted with sequins, bugle beads and fine chains, as well as red-carpet-worthy floor-length gowns featuring gold and silver appliqué lace, jacquard and chevron sequins inlaid on bare tulle.

At the more quotidian end of the scale, an autumn trend for cosy knitwear emerged, given an irreverent twist by the three designers behind the rising Sister by Sibling label. Their heroine for autumn 2013 is Paula Yates, whose spirit came through in ironic chintz-smattered cardigans in blue and pink, picked out with sequins and splattered with black polka dots. The punkish purlers have hit their stride between outrageous and outright commercial. In particular, a ribbed jumper with a graffitied portrait of Marie Antoinette should be a hit.

There were more retro woollens at Orla Kiely, and from Christopher Raeburn duffel coats, parkas and jackets. Fashion Week continues today, with Whistles, Topshop, Mulberry and Vivienne Westwood.