Royal watchers did a double take Saturday night in London, when Prince Charles's companion, Camilla Parker Bowles, sat in full view of the public in the royal family box as the Windsors watched the first in a series of concert programs honoring Her Majesty's 50 years on the throne. In America, PBS broadcast the performance, which featured classical music selections. Not that Parker Bowles, 54, sat cozily with Charles, 53. He sat in front with his Mum and Dad, while she was relegated off to the side and to the rear, with Charles's sister, Princess Anne. Dressed in pink, Parker Bowles curtseyed as the Queen, 76, entered the box, according to the British Press Association. That the Queen invited her to attend in the first place is being viewed as a significant step forward in Charles's campaign to gain acceptance for his longtime mistress, who was purportedly the bane of the late Princess Diana's existence. "There were three of us in this marriage," Diana famously once said, "so it was a bit crowded." Monday will bring another Golden Jubilee concert to the Palace, this one featuring Ozzy Osbourne, Paul McCartney, Brian Wilson, Phil Collins and other rock stars. Yet preparations for it were stalled Sunday, when a mysterious fire blazed for about 90 minutes within the Palace compound. No injuries were reported, said NBC News. Still, a Palace spokesman assured Reuters, "There is absolutely no question of (the show) not" going on.