David Cameron, U.K. prime minister and leader of the Conservative Party, speaks to employees as he visits Kelvin Hughes Ltd., a navigation and surveillance equipment manufacturer, while campaigning for votes ahead of the May 7 general election, in the Enfield district of London, U.K., on Tuesday, April 28, 2015. U.K. economic growth slowed more than economists forecast in the first quarter, dealing a potential blow to Cameron's claim that his Conservative Party is best placed to manage the economy's recovery. Photographer: Simon Dawson/Bloomberg via Getty Images