US President Barack Obama has arrived in Britain, where he is set to wade into the poisonous Brexit debate and have lunch with Queen Elizabeth II. Air Force One touched down at London Stansted Airport, northeast of the British capital, at around 9:45 pm (local time), beginning what is Obama's fifth and likely final presidential visit to the kingdom. The president, along with First Lady Michelle Obama, will pay tribute to the queen, who turned 90 yesterday, when they meet at Windsor Castle, west of London. "The president has very much enjoyed his engagements with the queen over the years," said top Obama foreign policy aide Ben Rhodes. The queen has reigned since 1952, during which time she has met with a string of US presidents from Harry Truman to Obama, who leaves office in January.

Pic: The Obamas with Queen Elizabeth II and Prince Phillip in 2011.