US President Barack Obama (L) looks on as Britain’s Queen Elizabeth II signs a guest book after a reciprocal dinner at the Winfield House in London, on May 25, 2011. Obama and his wife Michelle enjoyed a regal welcome from Queen Elizabeth II, who has met every US president but one since the 1950s. Obama’s visit, the second stop on a European tour, comes as Britain seeks to prove its staying power despite fading military might and Washington looks to retool its decades-old alliance with Europe as a catalyst for global action. AFP Photo/Jewel Samad (Photo credit should read JEWEL SAMAD/AFP/Getty Images)