David Cameron has opened his speech at the Conservative Spring Forum by saying that his party came to power in "perilous" times and that it was "wrestling with historic debts".
He added: "We are here to fight, we are here to win and we have never been more up to the task of turning our country around."
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Greater Manchester Police said "inquiries are ongoing to fully understand the circumstances of the incident."
The US president enjoyed rousing support for his political agenda as a formerly hostile audience cheered his plans in office to the rafters.
The former leader said the party needed to learn lessons after his successor Paul Nuttall failed to unseat Labour in a hard-fought campaign.