16/02/2012 10:43 GMT | Updated 22/05/2015 10:12 BST

It's Official (Nearly): Sienna Miller Shows Off Her Growing Baby Bump

It's official (nearly): Sienna Miller shows she IS pregnant as she shows off her growing baby bump
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She may have been keeping mum about it, but there is no doubt at all that Sienna Miller is VERY pregnant.

The secretive star hasn't breathed a word about her pregnancy, despite reports that she told close friends about her impending arrival before Christmas.

But her secret is most definitely out – and proud – now. The actress stepped onto the red carpet at "The Ever Changing Face of Beauty'" W Magazine opening reception yesterday.

She shocked photographers Beyonce-style by whipping off her coat and exposing her growing belly.

Sienna and Tom Sturridge - who started dating last year after she finally split from Jude Law - have refused to talk about the pregnancy.

But Sienna's sister Savannah confirmed the baby news in January, telling Vogue magazine: "She is doing really well and we are all really happy about it, Tom is an amazing guy."