The American President swept into the south today for a special birthday lunch with the Queen.
Barack Obama, accompanied by the first lady - arrived by helicopter at Windsor Castle. They were greeted by her majesty and the Duke of Edinburgh who were waiting in the Berkshire rain.
But Mr Obama also flew straight into a political storm as he used his last official visit as president to urge the UK to stay within the EU.
With more from Windsor, here's Divya Kohli.
Windsor Castle is to undergo a multi-million pound makeover.
The Royal Residence in Berkshire is sharing a £37m pound investment by the Royal Collection Trust. The work will open up more of the castle and create a special learning centre.
The works, known as the Future Programme, will start next year. The castle will remain open to visitors throughout the development.
Thousands of people have been applying for free tickets to help celebrate the Queen's birthday in Windsor.
Tickets for the celebration on the Long Walk in May sold out within hours in November. But a ballot of 5,000 tickets opened to the public yesterday.
The Long Walk will offer the opportunity to be involved in a pre-performance party on the final night of the event and to watch a live-screening of the ITV broadcast from the iconic Long Walk.
The show will tell the remarkable story of The Queen's life encompassing a reign spanning more than 60 years, starting from when she was born in 1926, through World War Two, to The Coronation in 1953.
Applications for the ballot can be completed online by filling out a short form, which can be found at www.hmq90.com or they can be applied for in writing to: Celebration on The Long Walk, The Old Booking Hall, Windsor Royal Shopping, Thames St, Windsor SL4 1PJ.
It is being billed as a huge party for the Queen - a star studded show in the grounds of Windsor Castle, to mark her Majesty's 90th birthday.
Now it has been revealed the event in May, which will be broadcast live on ITV, will be hosted by Britain's most popular TV duo Ant and Dec. As Rachel Hepworth reports, preparations are well under way.
The interviewees are: Simon Brooks-Ward, Director of the Queens's birthday celebrations; the singer Katherine Jenkins; Pau Roach, Windsor & Eton town manager; and Julia White, Windsor Visitor manager.
The Queen will be at Windor today presenting new colours to the Welsh Guards. her Majesty will then be join by the Duke of Edinburge and Duke and Duchess of Cornwall at a Regimental garden party in the grounds of the castle.
We've been at Windsor Castle today looking at how the staff are preparing for Christmas. Watch ITV News Meridian over the coming days to find out more!
An exhibition at Windsor Castle gives a new insight into the life of Queen Victoria, who has often been portrayed as a stern woman in black who was 'not amused'. Now documents show she as a very 'human' Queen, with plenty of passion.
Pages from her diaries are on show, as well as love letters, and important royal documents that date back from 1914. ITV Meridian's Divya Kohli got a glimpse of the new collection from the Royal Archives .