From uDiscovermusic.com:
The Supremes were the undisputed queens of Motown, and superstars around the world, when they crossed the Atlantic for a very special engagement on November 19, 1968. Diana Ross, Mary Wilson, and Cindy Birdsong performed in front of several members of the British Royal Family at the Royal Variety Performance in London.
The trio had been moving in such exalted circles for some time. In February of that year, the Duke and Duchess of Bedford had given a party to honor the Supremes at the Club Dell’Aretusa in Chelsea, London, where guests included Tom Jones, Mick Jagger, Marianne Faithfull, Michael Caine, and Lynn Redgrave.


At the time, the Supremes had, rather surprisingly, not had a UK Top 10 single for over a year, and “Some Things You Never Get Used To” had peaked outside the Top 30 in the summer. Nevertheless, their double Greatest Hits LP had topped the UK chart for three weeks earlier in the year, after doing the same in the US for five.
So the royal engagement was a memorable occasion, and Wilson, in her autobiography Dreamgirl, wrote: “The real highlight of this trip was the Royal Command Performance we gave before Princess Margaret and Lord Snowdon, the Queen Mother, Princess Anne and Prince Charles at the London Palladium.”


Reflecting the social mood of the time, and the heightened racial tension that existed in the US, Ross won rapturous applause when, in between the Supremes’ songs, she performed a monologue urging tolerance between races. “There’s a place for us. A place for all of us. Black and white, Jew and gentile, Catholic and Protestant,” she said. “So was the world of Martin Luther King and his idea. If we keep this in mind, then we can carry on his work.” Dr. King had been assassinated in Memphis some seven months earlier.
The show also featured such fellow performers as Sacha Distel, Engelbert Humperdinck, comics Frankie Howerd and Mike Yarwood, and British entertainer Petula Clark. She took to the stage in a white evening dress that weighed a daunting 40 pounds.
Mary Wilson also recalled the Supremes’ meeting with the royals. “Princess Margaret walked up to me, extended her hand, then — so quietly that no one else could hear — she whispered in her prim, high-pitched voice, ‘Is that a wig you’re wearing, Mary?’ I did all I could to suppress a giggle.”