With two public holidays from Thursday and then the weekend, British restaurants and retailers are hoping for a timely sales boost, after a difficult period including the Covid pandemic.
Supermarket chain Co-op predicted "a bigger sales period than Christmas".
On The Mall, a red-paved avenue leading to Buckingham Palace, royal enthusiasts from far and wide have been camping out, despite heavy downpours.
"It's the only way to make sure that you are at the front of the barrier when that royal coronation coach goes past, that golden coach," Mary-Jane Willows, 68, from Cornwall, southwest England, told AFP.
"It will be the most magical moment," she said.
But with Prince Charles taking over more of his mother's duties for occasions of state, there is a sense that the first -- and possibly last -- Platinum Jubilee in British history marks a turning of the page.
A poll for The Sun newspaper this week gave the queen a 91.7-percent approval rating. Charles commanded only 67.5 percent, behind his son Prince William on 87.4 percent.
In Australia, where the queen is also head of state, new centre-left Prime Minister Anthony Albanese has appointed an "assistant minister for the republic" to steer what he has called an "inevitable" transition.
Unlike the vocal Charles, the queen has rarely expressed an opinion in public, and her sheer longevity means that she has been a fixture of the life of nearly every Briton alive.
She has overcome numerous family traumas, including Charles' very public split from Princess Diana and personal heartache when her consort Prince Philip died aged 99 last year.
The jubilee is being seen as a chance for the nation to give thanks to the queen publicly, after social distancing last year prevented crowds at Philip's funeral, when she herself had to mourn alone.
The celebrations kick off Thursday with Trooping the Colour, a military parade that has officially marked the British monarch's birthday for centuries.
A fly-past will include Spitfires, the iconic fighter plane that helped win the Battle of Britain and fend off Nazi Germany in 1940.
The aerial display is expected to be watched by the queen and senior royals from the balcony of Buckingham Palace.
Balcony numbers have been limited to "working royals" only, leaving no place for self-exiled grandson Prince Harry and his American wife Meghan, nor Elizabeth's disgraced second son Prince Andrew.
Patriotic nostalgia runs red, white and blue throughout the festivities, culminating in Ed Sheeran singing "God Save the Queen" in front of Buckingham Palace on Sunday.
Participants in a giant public parade through central London earlier Sunday will be familiar to anyone acquainted with British popular culture since 1952.
But Bollywood dancers and a Caribbean carnival will also reflect the changes in British society since then, from one that was predominantly white and Christian, to one that is multicultural and multi-faith.
