Prince Charles didn’t seem to mind, however, and was soon sharing a joke with the rock star and his wife, who joined him in celebrating the opening of the new Prince’s Trust offices in London’s financial district.
When Prince Charles asked how Rod’s voice was, the singer replied that it was "improving with age" before his wife quipped "like a lot of other things."
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Rod later explained that the couple had been delayed by traffic, but that he always tells his children to be on time.
"I wish I had my own police escort," he joked. "I would always be on time." Protocol dictates that members of the Royal Family arrive last for a public engagement.
Rod and Penny became ambassadors for the Prince’s Trust ten years ago. The trust provides practical and emotional support to young people who need it the most.
"We are able to inspire and encourage our children, who have a strong support system and financial support," said father-of-eight Rod. "But what about the children that don’t have that support system? The Prince’s Trust is a real helping hand. "
Rod was attending the event on a break from the Rod Stewart Time Tour 2013. He will next take to the stage at the Liverpool Echo Area on 17 September.