London Mayor Boris Johnson, heptathlete Jessica Ennis, LOCOG chair Sebastian Coe and Omega President Stephen Urquhart at the launch of the Omega countdown clock in Trafalgar Square; Crown copyright Read more: <a href="http://www.culture.gov.uk/news/news_stories/7953.aspx" rel="nofollow">www.culture.gov.uk/news/news_stories/7953.aspx</a>