David Cameron has pledged an in-out referendum on Europe in 2017, and says he will not lead the country if he cannot guarantee to provide the vote.
The prime minister's comments, made on BBC One's The Andrew Marr Show, suggest he would not lead a minority government should the Conservatives fail to secure a parliamentary majority at the 2015 General Election.
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Mladic, now 75, was the military commander of Bosnian Serb forces in the 1990s, who fought against the Bosnian Croat and Bosniak armies.
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His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."