2016-04-22T125127Z_1443764479_D1AESZVMAHAA_RTRMADP_3_BRITAIN-ROYALS-OBAMA
U.S. President Barack Obama and first lady Michelle Obama are greeted by Queen Elizabeth II and Prince Philip, Duke of Edinburgh upon their arrival for lunch at Windsor Castle in Windsor, Britain April 22, 2016. REUTERS/Kevin Lamarque

President Obama and his wife Michelle arrived by helicopter at Windsor Castle on Friday (April 22) and were greeted by Queen Elizabeth, who turned 90 on Thursday, and her husband Prince Philip.

They will lunch privately at the castle, before Obama heads to London for a meeting with Prime Minister David Cameron.

Obama entered into the debate over Britain's upcoming referendum on European Union membership, arguing that the country should remain within the bloc.

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