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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The London Mayor insisted he was "not saying that nationalists are somehow racist or bigoted" after outraging SNP supporters.
Weather conditions remain wet and windy through the weekend
Jade Dunne, 29, has been charged with owning a dog dangerously out of control resulting in the death of Dexter Neal at her home in Halstead.