The banner is a joint initiative between prominent Londoner Kent Gardner and New Zealand agencies based in New Zealand House.
The central location means the silver fern can be seen from key vantage points throughout the city and Olympic venues. The banner will be present for the duration of the Olympics.
At the unveiling Mr Gardner said the silver fern showed the support of the New Zealand Olympic team in London. "We're here to show we are 100 per cent behind our Olympic team and we're here to show everyone in London and worldwide that New Zealand is here for the Olympic Games."
Watch the video of the unveiling of the silver fern by Kent Gardner here on you tube.