Queen's 90th birthday: Why Windsor is the monarch's party place
It is no surprise the Queen has chosen to spend her 90th birthday at Windsor Castle. But why does it fit the bill?
She has several royal residences, including Sandringham and Balmoral. However, it is to Windsor that she returns most weekends and is, it is believed, the place she most thinks of as home.
In 1931, when Princess Elizabeth was five years old, her grandfather George V gifted the Royal Lodge to her parents, the (then) Duke and Duchess of York.
The family used the 30-room mansion on the Windsor estate as their country retreat.
Not long after the outbreak of World War Two, it was decided that the safest place for Elizabeth and her younger sister Margaret was Windsor Castle and that would be where they would spend the majority of the war years.
Windows had been sandbagged, lightbulbs were dimmed and many of the artworks moved. It functioned as their home, school and playground.
Each year, the youngsters would enthusiastically take part in a Christmas pantomime. The first was Cinderella in 1941, with Elizabeth as the prince and her sister in the title role.
Elizabeth was 13 years old when war broke out and 19 when it ended. Much of her growing up was done behind Windsor Castle's thick walls.
She attended her first ball in 1941 and on her 16th birthday she became Colonel of the Grenadier Guards, carrying out the first of a lifetime of military inspections.
Queen's 90th: What's happening and when?
- 21 April - She will unveil a plaque on Windsor's Queen's Walkway, before lighting the first of a chain of beacons. Gun salutes will also be held across the UK
- 12-15 May - Celebrations featuring hundreds of horses and performers in the grounds of Windsor Castle
- 10 June - A national service of thanksgiving at St Paul's Cathedral
- 11 June - The annual Trooping the Colour at Horse Guards Parade
- 12 June - The Queen will host a street party for 10,000 people in the Mall
Royal biographer Christopher Warwick says her affection for the castle can be traced back to those years: "It was a place that was very much home to the Queen and to her sister for a very long time and that cemented the emotions and attachment that she has to a place she loves dearly."
During her many years as Queen, Windsor has continued to play a central role. Except during the summer and Christmas breaks in Balmoral and Sandringham respectively, the Queen spends most weekends at Windsor.
The vast grounds allow her plenty of opportunity to exercise the dogs and ride her horses. The Duke is the official Ranger of Windsor Great Park, responsible for its protection and maintenance.
It is the place the Queen's youngest son, Edward, chose to marry Sophie in 1999. Prince Charles had his marriage to Camilla blessed here in 2005. It is also where the Queen's parents and younger sister are buried.
Footage from November 1992, after a huge fire destroyed large parts of the castle, showed the Queen, concern etched on her face, inspecting the damage.
Warwick says her reaction to the fire indicated how much Windsor Castle means to the Queen: "It was devastating, [it] would have mattered incredibly to her as this was her home going up in flames."
The fire, started by a spotlight shining on to a curtain, burned for 15 hours and affected around 100 rooms.
That year also saw the breakdown of three of her children's marriages. The fire was the final low point in what she memorably referred to as her "annus horribillis".
The Queen agreed to foot much of the repair bill, which ran to almost £40m. Buckingham Palace was opened to visitors during the summer months to generate extra income.
The Windsor fire and its aftermath also sparked fundamental changes to the royal finances, leading to the agreement that the Queen should pay income tax on her private income.
As it has done over the past 1,000 years, Windsor Castle is adapting to modern demands. An improvement programme costing £27m has just been announced which will enable the site to accommodate even more visitors.
They currently number more than one million each year.
For Windsor locals, living next to the Queen does mean having to navigate around hordes of tourists on the high street and the regular road closures to allow the Changing of the Guard.
But most residents see it as a small price to pay for sharing a hometown with Britain's longest-reigning monarch.
Tina Saw, who has lived in Windsor for 30 years, said: "She is very much a part of the fabric of Windsor.
"Everyone feels she is a very special lady and is close to the hearts of everyone. She is very much loved."
Locals and visitors will have the chance to wish her a happy birthday when the Queen and the Duke go on a walkabout in the town.
The best spots will have been bagged early, however, as people are expected to have camped overnight.
In the evening, the Queen will light a beacon in Windsor Great Park, which will be the first in a chain of 1,000.
For the world's most travelled monarch, it seems fitting that what is effectively a huge line of birthday candles will be lit from her home to Britain's borders and beyond.