ITV News' Libby Wiener reports from Sao Paulo in Brazil where Prime Minister David Cameron is on a two-day visit.
The Conservative, who appeared on America's Late Show with David Letterman on Wednesday night, was quizzed by the veteran host over his knowledge of British history.
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Footage showing the "truly shocking" moment a teenager was stabbed to death as he rode his bike with friends has been released.
Drinking three to five cups of coffee a day could reduce the risk of clogged arteries and thus heart attacks, a study has found.
There are five million British expats across the globe. Many have a vested interest in May's election and many still have the right to vote.