EXCLUSIVE: Tom Selleck's Biggest Regrets Revealed As 80-Year-Old 'Seethes' Over Being Booted off 'Blue Bloods' And Its Spin-Off Show

At 80 years old, Hollywood's favorite mustachioed hero is still making hearts flutter.

Tom Selleck, the towering star of Magnum, P.I. and Blue Bloods, celebrates his milestone year with the same mix of charm, humility and rugged charisma that made him a household name in the 1980s, but RadarOnline.com can reveal beneath it all is a mass of regrets and rage.

"I'm proud of my work, I still love what I do, and I have my family," Selleck has said. "I've been enormously fortunate."

However, like anyone else, he's got regrets about his professional and private lives.

Selleck, who was born in Detroit and moved to L.A. with family, won a spot on the University of Southern California basketball squad after playing at Los Angeles Valley College.

But he reportedly got into only seven games in 1965-1966, scoring only four points, which is why he was forced to quit his dream and eventually turned his attention to acting.

One amazing Hollywood opportunity that slipped through Tom's fingers was the role of Indiana Jones in Raiders of the Lost Ark.

Selleck was originally cast as the whip-snapping hero. But fate had other plans. Just as George Lucas and Steven Spielberg came calling, Magnum, P.I. was picked up for a series, locking Selleck into his TV contract.

"I couldn't get out of my contract to do Magnum, and the role went to Harrison Ford instead," he recalled. "Was I disappointed? Of course. I could have done both Magnum and Indiana Jones, but CBS wouldn't let me. But Magnum turned out to be a pretty good consolation prize. Things worked out pretty well for me and for Harrison, I think."

Karen Allen, who played Marion Ravenwood in Raiders, said: "Tom wasn't just considered, he was cast initially. He had the role. I have run into him several times since then ... I think one of the great regrets of his career is not having the chance to play Indiana Jones."

When he got the call that he was invited to the White House to meet Princess Diana in 1985, he was flattered – but it led to another of Selleck's regrets... this time over not having taken dance lessons.

"Well, my publicist called. I’m in Hawaii, so Washington, D.C.'s pretty far away and we're in production [on Magnum, P.I.], but she told me about it," Sellech recalled.

He went on: "I said, 'Gee, that’s very flattering. I don't know how I could get there though.' And she said, 'Look, this is Princess Diana's personal guest list and there's only three actors on it: you, Clint Eastwood and John Travolta.'

"That was very flattering. Of course, I'm very nervous, I write about Clint and I hiding in the corner. We figured they were going to ask us to dance.

"I do remember dancing with her. I just remember apologizing that I never (learned) to dance. She was gracious.

"I skipped cotillion – they taught you how to dance and manners and everything else. My older brother went ... I managed to skip it, but then all I could do dancing was box step like we did in high school dances… I wasn’t about to dip Princess Di. So I just talked. But she was very gracious about it."

In the late 1980s, at the peak of his Magnum fame, Selleck did the unthinkable: he walked away from Hollywood stardom to focus on his personal life, even though the series was still a hit.

"Nobody wanted to cancel it," Selleck admitted.

But he chose to step back and concentrate on his second wife, Jillie Mack, now 67, and their daughter, Hannah.

His first marriage, to Jacqueline Ray, had crumbled amid the frenzy of his TV megastardom, and it left him with deep regrets.

"I wish I'd known better, earlier" he said.

The sudden fame and temptation that came with filming in Hawaii proved too much for his marriage.

Ray had stood by him in the lean years, but as one insider put it, she "couldn't stand the pain of seeing Selleck have a good time with other women" after he "fell in love with the island and with the island girls."”

That taught him a painful lesson about the cost of putting career before family. Determined not to make the same mistake twice, Selleck changed his life.

In 1988, he quit Magnum, P.I. and fled the Hollywood glare for the quiet of a California ranch, seeking dirty hands and honest work over the glamour of red carpets.

"My relationships and my ranch keep me sane," Selleck said, describing the 65-acre Ventura County spread where he and his family settled. "I've always treasured the balance between work and time with my family. It's always about them."

After a few quieter years in the '90s (barring memorable cameos like his stint on Friends), Selleck came roaring back to television in 2010 with Blue Bloods, the CBS police/family drama that proved to be a second act as triumphant as his first.

As NYC Police Commissioner Frank Reagan, the patriarch of a tight-knit Irish-American family of law enforcers, Selleck once again struck TV gold. The Friday night series became a staple for millions of viewers – especially fellow seniors, who found comfort in the Reagan clan's weekly dinner table sermons and Selleck's steady hand with his family.

But after 14 seasons, Blue Bloods was canceled – and it was tough for Selleck, who battled with the CBS brass, but lost.

Still, he's grateful it lasted so long – saying: "I never thought I'd be lucky enough to do a show that had that long a run."

He has since been sent seething over the ultimate betrayal costar and former protégé Donnie Wahlberg is stealing his beloved TV show, RadarOnline.com has already revealed.

The 80-year-old former Magnum, P.I. star bitterly fought CBS execs to keep his hit cop show on the air – but lost.

Now sources tell us he hit the roof when he learned Wahlberg will be the star of the show's newly-announced spin-off Boston Blue.