UK prepares for state visit of Barack Obama

US President Barack Obama will pay a three-day state visit to the UK this week.

The American leader and his wife Michelle are to stay in Buckingham Palace as guests of the Queen.

Some of the heaviest security measures ever seen will be put into operation when Mr Obama arrives in London on Tuesday, just three weeks after he gave the order for the operation which killed Osama bin Laden.

The heightened precautions come amid fears of a revenge attack by extremists over the al Qaida leader's death, with security services warning of the need for the world to remain vigilant.

The White House has said that the visit will be an important opportunity for Mr Obama to reaffirm the strength of the "special relationship" between Britain and the USA.

"The US and UK of course enjoy a special relationship," said deputy national security adviser Ben Rhodes. "There is no closer ally for the US in the world than the UK.

"We are in absolute alignment with the British on a range of core international security interests and, of course, our deeply shared set of values that have tied us together for many decades."

The Obamas, who fly to Ireland tomorrow, will leave Dublin for the UK on Tuesday morning and head for Stansted Airport where they will be greeted by the Prince of Wales and the Duchess of Cornwall.

They will be given a full ceremonial welcome in the garden of Buckingham Palace by the Queen and the Duke of Edinburgh, followed by a state banquet in the Palace ballroom in the evening.

The couple are already well acquainted with their royal hosts.

They hit it off and shared jokes during a reception ahead of the G20 summit two years ago.

The Queen and the First Lady acted like old friends when they put their arms around each other at the end of the event.

This state visit - the first since George W Bush's in 2003 - is being seen as something of a sweetener for the Obamas after they missed out on an invitation to last month's royal wedding.

It is not yet confirmed whether the new Duke and Duchess of Cambridge, who are due back from their honeymoon in the Seychelles this week, will play any part in the state visit.

Mr Obama described how William and Kate's wedding left America mesmerised, and indicated he watched part of it himself when he met the Prince of Wales at the White House earlier this month.

The President and his wife will get their own first-hand look at the royal wedding venue - albeit a month too late - when they visit Westminster Abbey during their stay.

Mr Obama will also hold talks with Prime Minister David Cameron at Downing Street and address both Houses of Parliament in Westminster Hall on Wednesday.

It is rare for a foreign head of state to address both Houses in Westminster Hall, usually this is reserved for British monarchs.

Heads of state are normally received in the Queen's Robing Room or the Royal Gallery.

Last September Pope Benedict became the third visiting dignitary to address both Houses in Westminster Hall since the Second World War, following South African president Nelson Mandela in 1996 and French president Charles de Gaulle in 1960.

In contrast to Mr Obama, former US presidents Bill Clinton and Ronald Reagan gave speeches in the Royal Gallery in 1995 and 1982 respectively.

President Bush was due to address both Houses during his 2003 state visit but this was cancelled due to anti-war protests.

Foreign Secretary William Hague is expected to use the visit to raise the case of Shaker Aamer - the last UK resident at Guantanamo Bay.

A return dinner will be hosted on Wednesday night at the US Ambassador's residence Winfield House for the Queen, Philip and other guests.