Palace staff members have put the finishing touches on the queen's ceremonial carriage, which will carry her through the streets of London in a royal procession.
Even the horses have to rehearse for their roles. In the end, it will look similar to the procession that took Queen Elizabeth to the opening of parliament last month.
The pomp and ceremonies of royalty are alien to many modern democracies. But the queen's longevity and the dignified way she carries out her duties appear to have cemented the monarchy's place in 21st-century Britain.
The city is being dressed up for the big party, including a huge poster of the queen and her family during her 25th-year celebrations.
MAN1: "I think the Diamond Jubilee is absolutely terrific. She's been the queen for 60 years. It's a celebration of all that she's given to this country, all the service she's given us over 60 years.
MAN2: "It's a fantastic occasion. Everyone is on a high. There's a lot of things to be not so pleased about going on in the world at the moment, so it's nice to have something that brightens up everybody's lives for a bit. So, yeah, it's great, fantastic, really looking forward to it.
Elizabeth is the only queen most Britons have ever known. She came to the throne as a young woman of 26, and pledged to serve for "all the days" of her life.
Those days have not been without controversy and tragedy, but at age 86, the queen has emerged as a hugely popular figure. Talk of ending the British monarchy has all but ended.
And when the queen joins the river pageant on Sunday, on board this specially built barge, and heralded by a boatload of bells, hundreds of thousands of people will gather along the river to cheer, just as they have throughout her jubilee year.