Togged out in tails, he showed how much he has changed since he first met the queen in 1965 - he and the other Beatles, sporting then-fashionable narrow lapels and skinny ties, prepped for that encounter by sharing a joint.
"My mum and dad would have been extremely proud - and perhaps they are," said the ex-Beatle bassist, garbed in sober, traditional tailcoat, his silver-streaked hair skimming his shoulders.
Keeping with tradition, McCartney bent down before the queen on one knee, and she dubbed him knight, laying a sword on each of his shoulders. Hundreds of fans, some wearing "Arise Sir Paul'' T-shirts, cheered his arrival and waited outside the palace until he emerged.
The queen made McCartney a knight, for his service to music, in her New Year Honors List. She officially bestowed the honor at Tuesday's ceremony.
Being a knight means he has the title "Sir'' and his wife the title "Lady." Linda McCartney, who is recovering from breast cancer treatment, stayed home, but Sir Paul said she was doing well.
Although the honor carries nothing beyond the title, it is still a coveted emblem of approval and standing in public life.
In 1965, McCartney and the rest of the Fab Four were dubbed Members of the Order of the British Empire - one step below knighthood. A lot has changed since then.
It was the height of Beatlemania, when the mop-haired rockers put Swinging London on the cultural map and attracted screaming hordes of fans everywhere they went. They dominated pop music with standards such as "She Loves You'' and "Yesterday''; they would go on to change it forever with albums including "Sgt. Pepper's Lonely Hearts Club Band'' and "The Beatles."
Battling stagefright before meeting the queen, the group took refuge in palace restrooms just prior to getting their awards - and calmed down by smoking marijuana.
Some other members of the Order of the British Empire sent their honors back to the queen to protest what they called the system's devaluation.
For McCartney, the days of marijuana arrests and psychedelic drugs in 1960s London are but a memory. He has settled down as a family man, an environmentalist and animal rights supporter.
One of the most successful pop stars of all time, McCartney also is a generous supporter of charities.
He has put some of his millions to good works, founding the Liverpool Institute of Performing Arts - officially opened by the queen this year.
The Beatles broke up in 1970, and the fourth Beatle, John Lennon, was killed in New York in 1980.
Sir Paul said Tuesday that the other surviving members of the Fab Four, George Harrison and Ringo Starr, make fun of his knighthood.
"They call me 'Your Holiness,''' he said.
AP PHOTO
Former Beatle Paul McCartney shows off a medal he received from Queen Elizabeth II in Buckingham Palace on Tuesday.