On June 3, Queen Elizabeth II will step — no doubt with sensible shoes — aboard the Spirit of Chartwell, a 210-foot luxury cruiser formerly owned by District-based National Geographic, in a royal procession along the Thames to celebrate her six decades on the throne.

The event has been billed as the crowning moment in the queen’s Diamond Jubilee, a year when Britons are raising a metaphorical pint to their long-serving head of state.

Currently docked in east London, the elegant cruiser is modeled after a 1929 railway carriage and has expansive hardwood floors, a grand piano and decorative designs made by the family firm that supplied artifacts for the doomed Titanic.

The fourth and final test that the vessel is river-worthy will be a rehearsal trip down the Thames on Monday (a date chosen because the river conditions are expected to resemble those on June 3). Assuming the Spirit of Chartwell proves it’s fit for the trip, the boat will retreat to a secret location for its final transformation into something resembling a royal barge from the 17th and 18th centuries.

There’s no escaping the jubilee, which is dominating the news with the queen offering gloved handshakes at events across the country. But the main merrymaking will occur during a four-day holiday weekend in June, and the festivities will come to a head with the 1,000-boat river pageant.

Philip Morrell, the owner of the Spirit of Chartwell, has better insight than most about what goes into organizing a flotilla traveling seven miles from Putney in west London to Tower Bridge in the east.

“There are so many people involved, you wouldn’t believe it,” Morrell said in a recent interview on his boat, as a workman’s head popped into view outside one of the ship’s panoramic windows. The man, who introduced himself as Simon, was outfitting the entire superstructure in 490 yards of gold-tinted film. Staring at his work, he muttered: “This better not fall off in front of 3 billion people, otherwise we will be at the airport trying to get out.”

Since January, Morrell has welcomed a small village aboard his yacht: awning makers, cinematographers, set designers, floral experts, sculptors, carpet manufacturers, throne designers, naval architects, embroiderers, Buckingham Palace officials, Clarence House officials and the police. The queen’s dressers? They popped in recently to jot down the colors and ensure there are no sartorial atrocities on the big day.

Although this summer’s pageant is being billed as the biggest of its kind in 350 years, it was once common to see royal processions on the Thames, which is sometimes called “liquid history” and was for centuries the main highway into Britain. For example, when Henry VIII’s second wife, Anne Boleyn, became queen, she traveled to her coronation on a barge along the Thames. When her husband had her tried for adultery, Boleyn traveled to her execution on a barge on the Thames.

One of the main organizers behind the river pageant is Adrian Evans, who has been planning the intricacies of the privately funded event for nearly three years. Despite his experience organizing carnivals, he said the Thames, a tidal river that rises and falls about 23 feet during the course of a day, adds “two or three dimensions to the problem.”

Also, he doesn’t want one boat after another to simply float by for an hour and a half, even if that’s the safest option. “That would get boring. We want to cluster boats, play music, encourage people to shout, wave and scream. . . . We’re working against standard practice on the Thames.”

Selected from a pool of more than 3,000 applicants, the flotilla will include tugboats, rowboats, kayaks, at least one boat from every Commonwealth country, and pleasure cruisers carrying 30,000 people. One barge will sprout water, another fireworks and another will ferry the London Philharmonic Orchestra. Ten film composers, including “Downton Abbey” composer John Lunn, have been drafted to write new music that will blare from various barges.

The lead boat, a floating bell tower, will carry eight newly cast church bells that will ring and be answered by churches along the Thames.

The Spirit of Chartwell needs to stand out from all of that.

The queen, her husband and other members of the royal family won’t be traveling lightly. Organizers are planning to haul tons of extras aboard, including a terra-cotta clay sculpture for the prow and hundreds of red, gold and purple flowers plucked from the queen’s gardens.

Morrell says the pageant staff members were attracted to his ship’s safety features, which include four watertight compartments and a powerful propulsion system that allows the boat to whip around 360 degrees on its own length and leave quickly should it come under attack.

Although Morrell, 66, won’t be aboard during the big day, his children — Tom, 27, and Lara, 25 — will be working as stewards, dressed in uniforms modeled on those worn by U.S. soldiers. Morrell’s children were schoolmates with the Middletons, he said, adding, “Tom says Pippa had the hots for him.” (Kate Middleton married Prince William last year, and her sister, Pippa Middleton, was maid of honor.)

While Morrell says it has been an “honor” to lend his vessel, it’s unclear whether it was a sound financial decision. His ticket-selling cruiser will start its season sailing down the Thames after the jubilee, three months later than normal. And although there might be a “Kate effect” on sales of almost everything Kate Middleton, now the Duchess of Cambridge, even glances at, a similar “Queen effect” has yet to drive bookings on his boat.

Morrell met the queen’s husband, Prince Philip, at a low-key event when he was 12, and he says what impresses him most about the royal family members are the reams of “events they do that aren’t heralded or publicized.”

It seems unlikely that the river pageant will fall into that category.