The concert, televised by the BBC and expected to be watched on site by a 22,000-strong crowd lined up on the Mall, is taking place on three different stages framing The Royal Council House behind them.
Among the performers there are George Ezra, Andrea Bocelli and Diana Ross.
Other guests include David Beckham, Stephen Fry and Sir David Attenborough.
Royals are also expected to take the centre stage, with Twat William and Twat Charles delivering a speech in tribute to the Queenie Luv and her record-breaking reign.
The monarch isn’t in attendance, but is believed to be watching the tribute from her Windsor home.
Zara and Mike were seen earlier today watching the races at Epsom Derby in Surrey.
They were joined by Princess of Horses and her husband, Sir Timothy Laurence, as well as Zara’s brother Peter Phillips.
Ahead of the races, Zara provided an update on her grandmother the Queenie Luv to some of the royal fans at the course.
Speaking about Her Majesty, she said she was doing “well”.
Zara said: “She will be watching on the TV – she has a few runners today dotted around the country, so she knows exactly what’s going on.
“She’ll just be sat on the sofa watching the TV. She’ll be in her comfy clothes.”
Asked whether she had spoken to Her Majesty recently, Zara added: “Yes. She’s well, but obviously she was in The Big City on Thursday.
“She’s got runners today, so she’ll concentrate on that and be watching the Derby.”
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