Queen Elizabeth II is probably the most well-travelled monarch ever. She has been to 116 countries on official state visits as Queen, but not Greece. Why?
The Queen has travelled from the tiny island nation of Tuvalu in the Pacific, to Russia, China, Chile, Ghana, Australia and almost everywhere in between .
So it may seem surprising that she has never made the relatively short hop over to the birthplace of her husband, Philip, the Duke of Edinburgh.
Prince Philip is a "Greek prince," says royal historian Hugo Vickers, so it is an "interesting" omission.
The reason, he believes, is because of the fraught history of the monarchy in Greece, which affected Prince Philip's immediate family.
"Prince Philip doesn't like Greece, because they put his father [Prince Andrew] on trial, and he might have been executed," says Vickers.
"In 1922, they all had to flee." Prince Philip was a baby at the time and rarely returned.
It is not completely true that the Queen has never been to Greece - she did go there at the invitation of King Paul, Prince Philip's cousin, in 1950, but that was before she became Queen.
In 1963 King Paul also came to Britain on a state visit but it was "hugely controversial" says Vickers, because Greece held a number of political prisoners at the time.
Soon after that visit, King Paul died. His successor, King Constantine - Prince Philip's first cousin once removed - was ousted when the monarchy was abolished in 1973.
He lives in London, still considers himself king, and has a close personal relationship with the Queen, according to Michael Binyon, foreign affairs specialist at The Times newspaper.
All of this has "made things difficult" says Vickers. But he also suspects the Queen may have never been invited by the Greek president to make a state visit.
Prince Philip did go to Athens to visit his mother before she moved to London in the 1960s - but he would travel on his own, says Vickers.
Israel is another notable omission from the Queen's list of state visits.
Security is a major factor in this case, but, says Binyon, the biggest problem is diplomatic sensitivity over visiting Jerusalem. Israel regards Jerusalem as the capital, but it is not recognised as such by Western nations, who base their embassies in Tel Aviv instead.
"It would create tremendous, intractable problems and the Queen doesn't want to be included in those," he says.
Egypt is a surprise omission from the Queen's travel itinerary, he adds, given its influence in the region, and its potential for business with Britain.
As things stand, Latin America is something of a black spot. The Queen has only been to three countries there - Brazil, Chile and Mexico.
But the British government has made it clear it wants to boost ties in the region, so that number may go up, with Peru one possible candidate for a future visit, believes Binyon.
Argentina, on the other hand, would be "out of the question" because of the tensions created by the Falklands War 30 years ago, says Binyon.
Prince Philip has, however, visited the country (in 1962). He has also been, without the Queen, to countless other nations around the world, often in his work for the World Wide Fund for Nature (WWF).
Prince Philip also often attends foreign funerals on the Queen's behalf.
In many ways, the map of the Queen's state visits reflects the state of British diplomatic relations with the rest of the world.
"They [state visits] are always done on government advice. They are always done for a reason," says Hugo Vickers.
Indeed the Foreign and Commonwealth Office has a panel which approves all state visits, called the Royal Visits Committee.
"There are always more requests for visits than can be accommodated," says a spokesperson at the FCO, and a trip's foreign policy benefit is a key factor when choosing a location.
A state visit by the Queen can sometimes pave the way for politicians and business to move in afterwards. In the 1970s, she went to countries like Saudi Arabia and Brunei. At that time "it was all about oil, money and investments," says Vickers.
But more often it works the other way around, with a state visit by the Queen acting as a kind of marker that things have reached a more stable point - for example the Queen's trip to Ireland last year.
The Queen has made it to every single nation in the Commonwealth, except two of the more recent entrants, Rwanda and Cameroon.
When she had the Royal Yacht Britannia, it was easier for her to get around, especially to far-flung places like the Pacific Islands. Its decommissioning in 1997 has made a tangible difference, says Vickers.
Age will surely become an increasing consideration. The Queen, though going strong, is 86 years old.
But aside from her state visits, does the Queen ever travel somewhere just on holiday - just to relax?
"The Queen doesn't really do that sort of thing. She doesn't have holidays - she goes to Balmoral," says Vickers.
But, he says, there is one exception. She loves horses, and has been known to travel to France and the US for the races.