The Queen and Duke of Edinburgh have arrived in Oman for the second leg of a five-day state visit of the Gulf.
The monarch was welcomed to the capital Muscat by the country's ruler Sultan Qaboos, after flying in from Abu Dhabi in the United Arab Emirates (UAE).
After greeting the Sultan, the royal party walked between two rows of soldiers who formed a guard of honour.
Speaking in Abu Dhabi, Foreign Secretary William Hague said the visit was a very effective form of diplomacy.
The royal trip is part of a government move to renew the UK's relationship with the Gulf Arab states.
Addressing an event celebrating UAE and UK relations, Mr Hague said: "A state visit is a very, very effective means of diplomacy... it's very, very powerful and the Queen is extremely effective at it.
"It puts the highest possible form of seal of approval on government-to-government activity."
Amongst her duties in Abu Dhabi, the Queen unveiled Lord Foster's modern design for the UAE's national museum.
The British architect showed the monarch his model for the Zayed National Museum, which will be built on Saadiyat Island off the Abu Dhabi coast.
Lord Foster, the creator of London's "Gherkin" skyscraper, said of the Queen: "She was very gracious and very complimentary.
"I think this is of great significance, the national museum is absolutely central to both culture and heritage of the United Arab Emirates."
Later the Queen, accompanied by Philip and the Duke of York, met hundreds of British expats who were waving union and UAE flags.
She also had a private meeting with Sheikha Fatima, the wife of the late ruler Sheikh Zayed.
The Queen last visited the UAE in 1979 as his guest.