DUBLIN, IRELAND - MAY 17: The Royal Flight containing Queen Elizabeth II and Prince Philip, Duke of Edinburgh arrives at Baldonnel Airport on May 17, 2011 in Dublin, Ireland. The Duke and Queen's visit is the first by a monarch since 1911. An unprecedented security operation is taking place with much of the centre of Dublin turning into a car free zone. Republican dissident groups have made it clear they are intent on disrupting proceedings.