Crowning achievement for Queen Elizabeth II

Queen Elizabeth II interrupted her annual summer vacation to mark this auspicious day, traveling down from her Scottish estate to open a new rail line. But the it wasn't about a train, it was about an 89-year-old queen who just keeps chugging along.

She is now the longest reigning British monarch, reports CBS News correspondent Mark Phillips.

After 63 years and 216 days on the job, the queen doesn't only understand how to do it, royal author Robert Hardman said -- she defined it.

"The queen is not elected. She is there to be, not to do," he said.

She has been just about everywhere and met just about everyone -- 11 of the past 12 U.S. presidents, somehow missing out on Lyndon B. Johnson.

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The U.S. may have shed the monarchy two-and-a-half centuries ago, but the heads of state have learned they had better get things right when she's around.

"She gave me a look that only a mother could give a child," former president George W. Bush said in 2007.

Elizabeth, it seems hard to believe now, was not destined be queen. She would have been a minor peripheral royal had her uncle not abdicated in favor of her father.

And she was but a tender 25-year-old when she became queen, being crowned the following year, and holding true to the promise she had made as a princess.

"I declare before you all that my whole life, whether it be long or short, shall be devoted to your service," she said on her 21st birthday on April 21, 1947.

It turned out to be long and active.

And while the train used to inaugurate the new line was a rolling anachronism, she, somehow, at 89-years old, is not. She has modernized the monarchy for the times, royal writer Roya Nikkhah said.

"The first monarch who opened her accounts to be scrutinized, the first monarch in this country who paid income tax, the first monarch to go with the times and introduce things like, you know, Facebook, Twitter," she said.

But Elizabeth has always known it's not the virtual, digital queen that matters. It's the real thing. To be queen of the people is to be seen among them.

Sometimes it's small crowds at suburban train stations, other times it's at big, official occasions.

"She's had to do lots of disagreeable things. Her government has made her have all sorts of horrible people to stay. Dictators, megalomaniacs," Hardman said. "She's had to go to places she doesn't want to go to do things she doesn't want to do. She always does it."

Despite that, she's smiled through it all.

"And she has had a very turbulent reign, if you think about it. Huge issues and problems within her family. Her children have been divorced. The death of Diana really rocked the monarchy, but she's come through it all. I think she's been a very dignified monarch," Nikkhah said.