The 'King's Speech' actress appears in a new campaign for the designer and while she never got to meet him while doing the ads - which were shot by photographer JUERGEN TELLER - she says it was a dream come true.
Helena - who is famed for her eccentric dress sense - told Elle.com: "I've never met Marc, but I've always admired his clothes. And he just said, 'Would I be interested?'
"Also just go with it and wear whatever I wanted, if I wanted to wear shoes that were different colours. In fact there were strict instructions, 'Please make sure she wears shoes that were different colours.' It came out like that.
"I just had a great day, I was amazed I was paid to do it. Frankly, I had a great day's fun of dressing up and playing around with Juergen. He's the least controlled, the least affected."
Helena, 45, also spoke about her unique sense of style, admitting it's not to everyone's taste.
She said: "My instinct anyway, unfortunately, as some people can tell, is to dress up. I do like dressing up, and I feel like you're channelling different people. They might be very unfortunate creations or sometimes more fortunate."