The rain cleared just before the royals appeared. First came Prince William, Princess Kate – in a blue dress by Roksanda – and Prince Harry, all riding in an open-top car. Also in the convoy: the Earl and Countess of Wessex and their daughter Lady Louise and Prince Andrew and his daughters Princesses Beatrice and Eugenie.
Speaking with the crowd, Kate "was saying that George opened the door today and said, 'It's not very nice out today mummy, is it?' She said 'No, it isn't George,' " shared Ella Hunter-Gibbs.
"She said she felt sorry for us in the rain. It has been a fantastic day, she was so nice."
"They are such a gracious couple," says Stuart Rivers, who was there representing the Sailors' Society organisation. "Her heart is for young people and we shared with her the work we do with young people around the world particularly supporting the children of seafarers with schooling."
Adds Mel Warman, also of the group: "It's so lovely that they want to hear what you've been doing. It's so lovely that people in that position have that real genuine interest in what we are doing around the world. She looked amazing, stunning."
A near neighbor in Norfolk chatted to Kate about their rural life. "Kate was saying she enjoyed taking the children to the beach," Charles Farrow says. "The beaches near us are perfect if you want to be quite quiet."
Farrow, who's vice-president of Norfolk and Norwich archeological society, asked William to join them. "He said, 'I don't know anything about archeology.' He was interested. I told him I would give him lessons."
Then, about 40 minutes later, the Queen and Prince Philip arrived in the Mall in their open-top Queen-mobile, her cerise dress making her stand out above the crowd.
William was called on to make a speech, and used the occasion to prose the woman he calls "granny."
"My family has had plenty of reason to celebrate since the Queen turned 90 in April: the Queen's strong health and relentless energy; her sharp wit and famous sense of humor; and the fact that The Queen remains very much at the helm of our family, our nation and the Commonwealth.
"The Queen at 90 is the one Head of State that world leaders can turn to for a first-hand perspective of the arc of history over the last six decades. At 90, The Queen is the leader of our country, who we all look up to in good times and in challenging moments to set an example, and to guide the way ahead.
"But the reason we are here today is to celebrate a role that matters just as much to The Queen as the one that she holds on the world stage.
"We are here to celebrate The Queen as Patron. Her commitment to the more than 600 charities to which she lends her name and support is unwavering."
And he added, "Before I finish, I hope you won't mind if I say a personal thank you to The Queen – and to do so on behalf of all her grandchildren – and great-grandchildren. Granny, thank you for everything you have done for your family. We could not wish you a happier birthday."
The Queen made her own thanks to the patronages who were there in their thousands. And ended with a joke about the year of celebrations.
"I much appreciate the kindness of all your birthday wishes, and have been delighted and moved by the many cards and messages I have received. How I will feel if people are still singing 'Happy Birthday' to me in December, remains to be seen!"
Stretching out almost as far as Her Majesty's eye could see on the historic Mall in London was a massive feast of food and wine from the picnic hampers given to the $215-a-head guests.
That meant 33,000 cups of tea, 20,000 slices of bread making the 40,000 sandwich triangles and more than 5,000 jugs of English spirit Pimm's. And 12,500 ponchos were packed too, in case of seasonal showers – and good thing they were, as rain did come down.
"You can't get more British than this. Rain, ice cream and Buckingham Palace," guest Claire Connick said.
They were at the party after buying tickets, rather than coming via a charity affiliated to one of the Queen's charities.
Wearing a long dress in a Union flag design was Lucinda Partridge, one of 18 supporters of the Anglo-Belgian Society which was set up in WWII to help Belgians fleeing the war.
"The weather doesn't deter us. It's fun – and been hugely well-organised," she said.
Also in the crowd: Prince Albert of Monaco, who chatted with Prince Andrew and his daughters and later to Prince Edward.
"I'm having a great time," he told reporters.
"It's wonderful to be here to celebrate with friends from Monaco and from the U.K."
Of the Queen, he adds, "Of course she's very respected the world over but we have such an important British community in Monaco.
"It's wonderful to be able to join our British friends in the celebration." He said about the atmosphere: "It's very relaxed and the rain hasn't hampered the spirits here at all."
The food was certainly bountiful. Provided by Marks & Spencer, the wicker hampers handed to each guest included a Scottish smoked salmon mousse, Pembrokeshire chicken salad, mini Piccalilli pork pie and British Windsor Apple Juice.
Giving the mousse an extra special royal touch, the salmon was slow-smoked over wood chips from an oak tree grown on the Queen's Sandringham estate in Norfolk.
The Queen and Prince Philip (who himself celebrated a landmark 95th birthday on Friday) were joined by Prince William, Princess Kate and Prince Harry.
The brainchild of Queen's eldest grandson, Peter Phillips, the Patron's Lunch celebrated the 600 organizations with formal links with the Queen.
"It's a chance for them to herald her contribution to their work, as well as to let the world know about all that they have achieved during her long life," he wrote in The Telegraph magazine last week.
At the center of the lunch celebrations was a carnival-like parade in which 1,500 volunteers performed themed tributes reflecting the Queen's 64-year reign – with the procession headed by a replica of the Queen's favorite, now-decommissioned, Royal Yacht, the Britannia. (The Queen famously shed a tear when the boat was decommissioned, not to be replaced, by the government in 1997.)
The Queen's son and immediate heir, Prince Charles, and his wife Camilla, Duchess of Cornwall took the celebrations out into the country by heading to Gloucestershire, for the Big Lunch – an annual event started by the Eden Project to get as many people as possible to have lunch together with their neighbors.