New York Police Department tactical police officers stand guard near the New York Stock Exchange on September 9, 2011 in New York City. Officials are stepping up security in New York and Washington D.C. a day after U.S. officials received a credible but unconfirmed terror threat to utilize car bombs on bridges or tunnels in New York or Washington. (Photo by Justin Sullivan/Getty Images)

A gallery assistant holds a print of an Andy Warhol artwork estimated to fetch 1,500 GBP in Bonhams auction house on November 25, 2011 in London, England. The auction of prints of works ranging from old masters to contemporary artists takes place in London on November 29, 2011. (Photo by Oli Scarff/Getty Images)

(L-R) Mollie King and Frankie Sandford of The Saturdays performs for a dress rehearsal before the first night of their “All Fired Up!” tour at The Bournemouth International Centre on December 1, 2011 in Bournemouth, United Kingdom. (Photo by Dave J. Hogan/Getty Images)

A gallery assistant holds a rare 14th century time-telling device device in Bonhams auction house on December 9, 2011 in London, England. The instrument, which dates from 1396 and was discovered in a shed in Queensland, Australia, is due to be auctioned on December 13, 2011 and is expected to fetch 200,000 GBP. (Photo by Oli Scarff/Getty Images)

Charlotte Roirdan from Lyon & Turnbull views a letter written by Mary Queen of Scots on March 8, 2012 in Edinburgh, Scotland. The 450 year old letter, unearthed in Blair Castle in Ayrshire, has been verified as the hand writing of Mary Queen of Scotts and has been valued at 3,000 GBP. The letter, dated March 20, 1554, relieves the then laird of Blair from his duties due to gout and will be put up for sale next week at an auction in Edinburgh. (Photo by Jeff J. Mitchell/Getty Images)

Emergency services continue to attend the scene of a multiple fatal collision near Junction 25 on the M5 motorway on November 5, 2011 near Taunton, England. At least 27 vehicles crashed on the northbound carriageway of the M5 near Taunton, causing several explosions. Police have confirmed that several people have been killed and 43 have been injured but emergency crews have as yet been unable to confirm cause of the crash. (Photo by Matt Cardy/Getty Images)

Artist Richard Neave admires the sculpture “Sprinting” that he created with Denise Smith on March 12, 2012 in London, England. The model shows the body of elite athlete, Richard Whitehead, and forms the centre piece at the Anatomy Of An Athlete Exhibition opening at the Hunterian Museum. (Photo by Bethany Clarke/Getty Images)