US president Barack Obama has paid a glowing tribute to the Queen, describing her as an "astonishing person and a real jewel".

He spoke after having lunch with the Queen and the Duke of Edinburgh at Windsor Castle and presenting her with a 90th birthday present - a reminder of her many visits to America.

Speaking at the Foreign Office, Mr Obama said the Queen "is truly one of my favourite people".

And he added: "She's an astonishing person and a real jewel to the world, not just to the United Kingdom."

Mr Obama said he had returned to the UK to "wish her Majesty, the Queen, a very happy 90th birthday".

He added: "Earlier today Michelle and I had the honour to join her Majesty and his Royal Highness, the Duke of Edinburgh, as their guests at Windsor Castle, where we conveyed the good wishes of the American people."

The President spoke fondly of the meeting, joking that he had "never been driven by a Duke of Edinburgh before", adding that the drive in the grounds of Windsor Castle had made for "very smooth riding".

He went on: "As for her Majesty, the Queen has been a source of inspiration like so many people around the world.

"She is truly one of my favourite people, and should we be as fortunate to reach 90, may we be as vibrant as she is."