KATCHING MY I: Sienna Miller looks fabulous in floral sundress as she launches the new BMW i3 in London

Monday 29 July 2013

Sienna Miller looks fabulous in floral sundress as she launches the new BMW i3 in London

PUBLISHED: 22:50, 29 July 2013 | UPDATED: 23:20, 29 July 2013

She's known her boho style and her quest to be green.

So Sienna Miller was the perfect choice to launch new electric car BMW i3 in London on Monday.

The actress showed off her slim figure in a floral sundress as she joined Hollywood star James Franco to unveil the vehicle at its global reveal.

Start your engines: Sienna Miller unveils the new BMW i3 at the car's global launch at Old Billingsgate Market on Monday

Fabulous in floral: Sienna looked summery in a floral sundress

Sienna and James were the big names in attendance at the star-studded bash at Old Billingsgate Market.

It was the first time the vehicle has been on display ahead of its November release, and will be the first car from BMW's new i sub-brand.

Speaking to the MailOnline about the vehicle, Sienna said: 'Being a new mother I feel it's very important to make green choices and create a better world for the future.

The big reveal: Sienna was joined by actor James Franco to unveil the new BMW i3

All the way from Hollywood: Actor James Franco looked dapper in a dark suit

Sitting pretty: Sienna perches on the i3 as she poses alongside James

'It's the perfect city car. Ooh double doors!'

James agreed: 'Going green is now cool. I'm really excited about this, it's about time we started taking care of the environment. It's fantastic. I feel like it's the future.

'I'm happy to be involved with something that's green. That's cool. I like the orange one and I think it will cope with the Hollywood Hills just fine.'

Among the stars in attendance was model Donna Air, who arrived solo without her boyfriend James Middleton, who may be spending time in Berkshire with new nephew Prince George and sister Catherine, Duchess of Cambridge.

Going green: Sienna has long championed environmental causes

Where's Uncle James? Donna Air arrived solo without boyfriend James Middleton

Mellow yellow: TV presenter Laura Whitmore showed some leg in a yellow mini dress

Mother-of-one Donna went for an unusual black ensemble of sleeveless top and skirt with circular detailing and a pair of eye-catching red and black heels.

Flashing some leg at the launch was TV presenter Laura Whitmore who wore a bottom-skimming yellow mini dress.

Former Britain & Ireland's Next Top Model judge Grace Woodward showed off her bump in a cream dress.

Tight: Socialite Peaches Geldof looked super slim in her black ensemble, while Sugababe Jade Ewen showed off her curves in a navy and green bodycon number

Bumping along nicely: Heavily pregnant stylist Grace Woodward showed off her bump in an unusual ensemble

The stylist, who is expecting her first child with husband Ken, tweeted: 'I look like a space matron in this dress. Like Nursey if Blackadder was set in the future. oh.'

Other guests included Peaches Geldof, Sugababe Jade Ewen, model Laura Bailey, socialite Poppy Delevingne and classical boy band Blake.

Providing the entertainment at the party were Jack Guiness and Amber Le Bon in the DJ booth.