To mark the occasion, she will meet-and-greet locals on a royal walkabout around Windsor, a charming city about 20 miles west of London and home to Windsor Castle, a royal residence.
The walkabout is an unmistakable message that the queen is still very much on the move. Indeed, as the Daily Telegraph noted, she carried out more engagements last year than William, Kate and Harry combined. The walkabout is also an example of the many ways the queen has put her own mark on the British monarchy. After she first tried it during a visit to Australia and New Zealand in 1970, walking among the crowds has become a fixture of royal events.
In the evening, the monarch will make another royal gesture and light a beacon. Hundreds of years ago, lighting beacons across the land was a way to communicate; today, the royals have adopted it as part of their panoply of traditions deployed on big occasions.
On Thursday evening, the queen will light the first of more than 1,000 torches or bonfires expected to be set ablaze across the U.K. and beyond. Beacons will be taken to the highest peaks in each of the four nations of the United Kingdom: England, Scotland, Wales and Northern Ireland.
During her birthday week, the queen, accompanied by the Duke of Edinburgh, will open a new bandstand near Windsor Castle and visit Windsor’s Royal Mail delivery office, where she will meet the Royal Mail choir (yes, there is such a thing).
On Friday, she’ll host a lunch for Barack and Michelle Obama, who famously caused a stir here in 2009 when she put her arm around the queen during a photocall.
“The message Buckingham Palace is giving out is, she is still working on her 90th birthday,” said Robert Lacey, a royal biographer.
But it’s not all work. Charles, the queen’s son and heir, is hosting a private dinner on her actual birthday, and Nadiya Hussain, winner of the popular TV program “The Great British Bake Off,” has said she's baking the queen an orange drizzle birthday cake.
Royal watchers say she will also likely go horse riding on the big day.
And there will be more celebrations to come. The queen celebrates two birthdays every year: her real birthday, on April 21, and an official one in June.