LONDON, UNITED KINGDOM - JULY 17:  Britain's Prime Minister David Cameron answers a question during a joint news conference with Italy's Prime Minister Enrico Letta in 10 Downing Street on July 17, 2013 in London, England. Mr Letta is here on a two-day visit and will later meet with Labour Party leader Ed Miliband at the Italian Embassy in London.  (Photo by Andrew Winning - WPA Pool/Getty Images)