Where exactly was the site of the house where the Queen was born? Have visitors been looking in the wrong place? And are the claims that the house was damaged in the Blitz correct?
The Queen was born on 21 April 1926 at 17, Bruton Street in Mayfair, London. Not a palace or a big estate or even a hospital, but a townhouse on a busy London street.
Her parents had moved into the house, belonging to her Scottish grandparents, the Earl and Countess of Strathmore, only a few weeks before her birth.
"It's a reminder of how the royal family was not as flush in those days. Money was an issue," says royal historian Robert Lacey.
Bear in mind, the Queen was not born to be Queen - at this point, as the daughter of the King's younger son, she was not expected to take the throne.
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Was the house 'Blitzed'?
The Queen's first home no longer stands - and there are widely-published claims that it was a casualty of air raids during World War Two.
But armfuls of documents in the British Library and other archives show that's incorrect. The 18th-Century townhouse was gone before the war had even started.
It was property developers, much more relentless than air raids, that really finished off the Queen's first home.
In 1937, a man in a top hat and frock coat had formally started the demolition of 17, Bruton Street, along with the destruction of many of the neighbouring buildings stretching around the corner into Berkeley Square.
There had been plans to build a hotel for the Canadian Pacific Railway, but the site was eventually cleared for an office and retail complex.
These were unsentimental times about architectural heritage.
Without a glimmer of regret, demolition gangs flattened what were described as "20 of the most historic houses in London".
A poignant drawing by the war artist Sir Muirhead Bone recorded workmen pulling down the facades of the elegant old buildings.
If there was any further doubt, a handwritten surveyor's note from May 1939, held in the London Metropolitan Archive, shows the closure of the file on the original 17, Bruton Street.
It confirmed that the old house had been demolished and "its site forms part of that upon which Berkeley Square House has been built".
Astrea, the firm currently running the Berkeley Square House site, says the new building was occupied by the air ministry, in the run-up to the outbreak of World War Two.
Is it now a Chinese restaurant?
But there's another frequently repeated claim about the Queen's birthplace - that the site is now a Chinese restaurant.
Even though it's widely reported it's not the full story.
The Hakkasan restaurant has the same 17, Bruton Street address. But so does an adjacent stretch of boarded-up offices. There's also a glass-fronted, corporate entrance and reception area in the same block.
All of this extended business block is built over what in the 1920s would have been a row of individual, private houses.
It might not be such a romantic story, but it's the rather anonymous corporate entrance that seems closest to the site of the original 17, Bruton Street. The site of where the Queen was born is now a sideway into offices in Berkeley Square House.
In the London Metropolitan Archive in Clerkenwell, there are bundles of old files and architects' drawings, with art deco lettering, showing the layout of the original house.
They show the lost house would have stood around this entrance area, with the frontage stretching down towards what is now a car showroom selling Bugattis and Bentleys.
This is confirmed by Westminster City Council whose planners say this can be plotted against the boundary lines of original properties on the other side of the street.
One end of the restaurant would have overlapped with the original house, and Hakkasan general manager Sharon Wightman says the royal connection is a "brilliantly interesting talking point, which goes down well with our guests".
But much of the Queen's old home is now replaced by the corporate glass of the entrance next door.
There are two plaques on an adjacent wall marking the birthplace, including one from Westminster Council. These have been moved around as the buildings have been altered and are at one end of the original site.
There's no official blue plaque because a spokeswoman for English Heritage says they have to be on original buildings - and, also, they don't put up plaques for living people.
Toby Cuthbertson, from Westminster's planning department, says this would have been a high-class, "first-rate" London property, five bays wide - but the very wealthy would have been another step up, in the type of houses that had names, rather than numbers.
When the Queen was born here in 1926, her royal grandparents came to see her on her first day. Queen Mary recorded in her diary that her grand-daughter was "a little darling, with a lovely complexion and pretty fair hair".
It's also where the Home Secretary William Joynson-Hicks hurried, as it was then still protocol that the home secretary was present for such a royal birth. He was considered such an authoritarian, he was nicknamed "Mussolini minor".
This was the house where the Queen's mother, Elizabeth Bowes-Lyon, had set out in April 1923 for her wedding to her shy suitor, the then Duke of York. They returned here for the birth of their first child almost exactly three years later.
The house was also in walking distance of the Harley Street practice of speech therapist Lionel Logue who, from 1926, helped the future King overcome his stammer.
No tourist trail
This would have been a Mayfair of upper-class parties and fashionable gatherings.
But it was also a politically volatile and divided time. The general strike was called only a few weeks after the Queen's birth and her grandfather, George V, had cautioned: "Try living on their wages before you judge them."
The Queen and her parents moved later that year to a bigger house in Piccadilly.
There were subsequent plans to convert the house in Bruton Street into offices, with architects' drawings showing how the rooms, including where the Queen was born, would have been panelled, partitioned and redesigned for office workers.
"The room on the first floor, in which the little princess was born, is one of the least ornate of all the rooms, but also one of the sunniest," read a newspaper account at the time.
But the house was demolished - and remains a curiously low-key site for such an historic place.
There can't have been many other private, family houses in London which were home to a future King and two Queens - yet the site is barely on the tourist trail.
"I think it reflects the general modesty of the Queen," says historian Robert Lacey. "She doesn't blow her own trumpet."
The site is still part of a royal estate, but these days it belongs to the estate of the royal family of Abu Dhabi - part of a portfolio of property in this part of London said to be worth £5bn.
The original 17, Bruton Street was managed in the early 1930s by Howard Frank, co-founder of the Knight Frank estate agency.
Simon Burgoyne, now working for Knight Frank on property in modern Mayfair, says this fashionable area was where landed families, with estates in the country, had their London townhouses.
"But after the war, no one could afford to keep these big, old, rambling buildings, so a lot of them were turned into offices," he says.
This has now come full circle, says Mr Burgoyne, with offices being turned back into luxury residential property. If the house had survived, it would have been worth well over £25m, he says, and possibly as much as £100m.
But the house was flattened in 1937 - and, in another unexpected turn, by then the young Elizabeth and her parents had moved into Buckingham Palace.
The abdication crisis of 1936 had seen her father take the throne as George VI, following his brother Edward VIII's plan to marry an American divorcee, Wallis Simpson.
Mrs Simpson had been followed by Special Branch officers during this political maelstrom and they had noted claims that she had had an affair with a car salesman called Guy Marcus Trundle.
In a final twist, the address where they found this "charming adventurer" was 18, Bruton Street, now, appropriately, part of the Bentley dealership.