"I don't think she's a big pop music fan," said Sir Elton John, backstage at the Queen's Diamond Jubilee Concert.
"I think she'll really like the opera singer, Alfie Boe. I think she'll like the pianist, Lang Lang. I don't know that she'll like us very much."
We may never know whether Her Majesty enjoyed the pop music played on the steps of Buckingham Palace on Monday. After all, she has had six decades to practice looking inscrutable.
But the monarch was visibly moved by the crowd's enthusiastic support for the Jubilee - and appeared close to tears when they broke into an impromptu chant of "Philip, Philip" for the Duke of Edinburgh, who had been taken to hospital earlier in the day.
The other members of the Royal Party were easier to read.
Princesses Eugenie and Beatrice danced in their seats to Jessie J; Prince Harry was rapt by Kylie Minogue's routine (and, perhaps, her outfit); and Prince William was spotted rocking out to Live And Let Die.
The three-hour Jubilee Concert, organised by Take That's Gary Barlow, was a proper Royal knees-up.
It certainly put paid to memories of the terrifyingly awkward "Party At The Palace", held for the Golden Jubilee in 2002.
That show was marred by moments of cheese (Brian May on the roof) and inexplicable collaborations (Brian Wilson performing Good Vibrations with Atomic Kitten, anyone?)
Barlow's show was worlds apart. Slick, pacy and as well-drilled as the changing of the guard.
Robbie Williams got things off to a rousing start, embellishing Let Me Entertain You with military pomp, courtesy of the Guards Drummers and Trumpeters.
"Ain't nobody here going to do it like me," he chanted - a bold claim when he was being followed by the crown jewels of British rock and pop.
The first half of the concert, held before the Queen took her seat, rattled through the noisier spectrum of chart pop, with Jessie J, will.i.am and JLS whipping the crowd into a frenzy.
But Sir Cliff Richard was the first act to unite the audience in a singalong, with thousands of Union Jacks being swung in time to Congratulations - from the Royal Box down to the front row.
"Red, white and blue - it was stunningly fantastic," he said afterwards,
"And when I looked down The Mall, the crowd seemed to go all the way up to the Admiralty Arch.
"I don't know how many people that represents but it's got to be hundreds of thousands. It's very humbling."
Sir Cliff was first of a quartet of knights to play the concert and, by and large, they received the best reaction.
Sir Tom Jones prompted what the first ever mass flamenco dance on the steps of the Queen Victoria Memorial as he launched into Delilah.
Sir Elton John, still recovering from a respiratory infection, was nonetheless in fine voice as he gave a delicately soulful reading of Your Song.
And Sir Paul McCartney wrapped up proceedings with a jaunty crowd participation version of Ob-La-Di, Ob-La-Da.
Other memorable moments included Annie Lennox's There Must Be An Angel, for which she sported a set of wings, and Grace Jones' hula-hooping her way through Slave To The Rhythm.
Alfie Boe and Renee Fleming also turned heads, performing West Side Story's Somewhere from the balcony of Buckingham Palace - a neat reference to Romeo and Juliet.
It wasn't just the music that impressed: A series of light projections beamed onto the walls of Buckingham Palace were spectacularly realised.
During Madness' Our House, the Palace was transformed into a row of terraced houses, with the windows and doors flipping open to reveal families dancing inside.
The concert's only awkward moment came when Stevie Wonder dedicated his song Happy Birthday to the Queen. Had he got mixed up between the Jubilee and a birthday party? Or was he getting his greetings in a little early for the Queen's official birthday in 12 days time?
Or perhaps he was giving a nod to the Commonwealth - fans watching the show on TV in New Zealand had of course just celebrated their own public holiday, marking the Queen's official birthday there.
Backstage was like a Commonwealth of Pop, as the stars happily mingled with one another, swapping stories and posing for photographs.
Their conviviality spilled over to the audience, where no-one was jostling for position or pushing their way to the front.
"It's a really nice atmosphere," said Cheryl Cole. "It just feels really English and pleasant."
"It feels really friendly," agreed Kylie Minogue. "People seem really happy. Even though it's been raining on and off, it's not seemed to dampen anyone's spirits."
On stage, the jokes were similarly good-natured - the Royal Box particularly enjoyed Lenny Henry's impression of Prince Charles.
And there was a wry smile when Jimmy Carr quipped that the Queen's 60-year-reign should serve as a warning that "you've got to plan for your future and you've got to get a pension.
"She's 86 and she's had to rent out her driveway to Gary Barlow!"
The highlight of the musical performances was undoubtedly the Jubilee Song, written by Sir Andrew-Lloyd Webber and Gary Barlow.
Opened by a 14-year-old soloist called Lydia, the simple, but emotive song packed a huge punch - particularly as the orchestra swelled for the finale.
The song saw musicians from across the Commonwealth take to the stage, including Kenya's Slum Drummers and the African Children's Choir.
"I can't believe myself. It's like I'm in heaven," said Joel, a percussionist with the band.
Asked who he would be watching on stage during the concert, Joel's answer was simple: "The Queen".
It was a sentiment shared by all of the night's performers, from the youngest wannabes to the most seasoned performers.
"What a fantastic job she's done," said Sir Paul McCartney. "She's a great example for Britain and she's a great family woman."
"She's stoic, she's brilliant, she's wise, she's funny. We're all very glad to be here," said Sir Elton John.
Rolf Harris was one of the few artists to speak directly to the Queen from the stage, calling her "a living testimony to the power of dedication, kindness, tolerance and loyalty."
"I hoped that I conveyed to the Queen everybody's intense love of her," he told the BBC afterwards.
"You could feel it welling up all around you."
Robbie Williams - Let Me Entertain You
Will.i.am and Jessie J - I Gotta Feelin'
Jessie J - Domino
JLS - Everybody In Love / She Makes Me Wanna
Gary Barlow and Cheryl Cole - Need You Now
Cliff Richard - Medley, including Dynamite, The Young Ones, Devil Woman, We Don't Talk, Wired For Sound, The Millennium Prayer, Congratulations
Lang Lang - Hungarian Rhapsody #6, Rhapsody In Blue
Alfie Boe - O Sole Mio / It's Now Or Never
Jools Holland and Ruby Turner - You Are So Beautiful
Grace Jones - Slave To The Rhythm
Ed Sheeran - The A Team
Annie Lennox - The Must Be An Angel
Renee Fleming - Un Bel Di Vedremo
Tom Jones - Mama Told Me Not To Come / Delilah
Robbie Williams - Mack the Knife
Gary Barlow et al - Sing
Shirley Bassey - Diamonds Are Forever
Kylie Minogue - Medley, including Spinning Around, Can't Get You Out Of My Head, Step Back In Time, All The Lovers
Renee Fleming and Alfie Boe - Somewhere
Elton John - I'm Still Standing, Your Song, Crocodile Rock
Orchestra - Beautiful Day (instrumental)
Stevie Wonder - Sir Duke, Isn't She Lovely, Happy Birthday, Superstition
Madness - Our House / It Must Be Love
Paul McCartney - Magical Mystery Tour, All My Loving, Let It Be, Live And Let Die, Ob-La-Di Ob-La-Da
All performers - National Anthem