Former NPR radio host Diane Rehm with her fiance, retired Lutheran minister John Hagedorn. The couple will marry in October. (Courtesy of Diane Rehm)

Diane Rehm had plenty of things she wanted to do after retiring last year — write, travel, launch a new podcast. Getting married was definitely not on the list.

So guess what? She just got engaged.

“Honey, I’m 80 years old, for God’s sake!” says the former NPR star with a delighted smile. “I’m shocked.” But “very, very happy.”

Rehm will marry John Hagedorn, a 77-year-old retired Lutheran minister, on Oct. 14 at Washington National Cathedral. “He’s so caring, so attentive, so warm,” she says. “Not only just to me, but to all of our friends and neighbors.”

The two met 28 years ago at a wedding for the daughter of a mutual friend. Both were married to others at the time, so it was a pleasant exchange but all but forgotten until Rehm received a letter from Hagedorn last summer.

He reintroduced himself and praised her latest book, “On My Own,” a memoir about her life as a widow (Rehm’s husband of 54 years, John, died in 2014). Hagedorn, now a widower, wrote that the book had really moved him.

“If you’re ever in Florida, please let me know,” he said. “I’d love to see you and take you for a cup of coffee.”

As it turned out, Rehm was doing a book-reading in Orlando for 1,500 fans. She emailed him with an invitation to the event, and Hagedorn drove more than three hours to attend, standing in line for two hours for a chance to speak with her.

Then the two shared what we’ll call “a moment.”

“We have a photograph taken, I sign his book,” she says. “He’s about to walk away and he turns around and looks at me. I turned around and looked at him. And something happened.”

It seems Hagedorn had been carrying a torch since they first met.

“Diane has lived in the back of my heart and soul since we first met 28 years ago,” he said in an email. “When the opportunity to meet again arose last June, I leapt at the chance. When our eyes met at the end of the meet-and-greet I said, ‘What just happened to my life?’ ”

An old-fashioned courtship ensued. Hagedorn asked if he could visit her in Washington, where they toured museums and restaurants. She gave him a chaste kiss on the cheek when he headed home, but that was it. “I wasn’t there yet,” she explains.

She, in turn, visited him in Lake Worth, Fla. (Her first question: “Do you have a separate guest room?”) They met each other’s children and were vetted by friends, all of whom approved of the match. Rehm’s best friend, Trish Vradenburg, who died earlier this month, joked that they were “the 80-year-old Barbie and Ken.”

Hagedorn started proposing on their third date, and Rehm answered: “No! Way too early!” She finally accepted two weeks ago. Instead of a conventional engagement ring, Hagedorn is refitting his grandfather’s antique topaz ring, a cherished family heirloom, for her.

The couple will have a commuter marriage: She’s keeping her home in Washington, and he will keep his house in Florida.

“At the end of Diane’s last book she wrote that at her age, there would probably never be another significant meaningful person in her life,” said Hagedorn. “But, ‘Never say never!’ I am blessed.”