George Clooney and Brad Pitt’s almost 30-year friendship was sparked by Princess Diana’s death, the Hollywood actors have revealed.

Pitt, 60, said his close friend and fellow Oscar-winner “first stood out” to him when he made a speech attacking the press after Diana was killed in a car crash in 1997 while she was being pursued by paparazzi.

“We’ve been in Paris in those same chases”, Clooney, 63, told GQ during a joint cover interview with Pitt from his French vineyard Chateau Miraval.

“The hunt? I can’t tell you, I can’t describe it to anyone. It was insane. You would have nine cars following you. They’re waiting for you,” Pitt said.

The Fight Club actor added: “Oh my God. And you stop at a stoplight and they all get out and it’s flash-flash-flash-flash-flash-flash.

“And you can’t see anything, and you can’t move because you’re trapped between cars at a stoplight. It’s a horrible feeling.

“It’s really invasive to know people are out there and they’re hiding in the bushes. It’s really a s-----, s----- feeling. And so George got up and commented on that after Princess Diana. And that’s when I saw: this guy’s got something that the rest of us don’t. Like, I saw the leader in that moment.”

After Diana’s death, Clooney accused magazines and newspapers of turning photographs into “bounty hunters” for buying pictures of celebrities and stars.

He told reporters at the Screen Actors Guild office in Los Angeles at the time: “If you weren’t hiding behind the profession of journalism, you would be an accomplice to a crime, and you would go to jail.”

Elsewhere in the GQ cover interview, Pitt likened being famous to being a “gazelle” being pursued in the animal kingdom.

“You watch those nature documentaries. There’s that one gazelle that gets caught off. And then the lions and then the cheetahs are chasing him. And then afterward if they escape, they go through the trauma, the shakes.…”, he said.

Clooney added that while some celebrities are able to return to normal life and walk around cities like New York without being followed, the interest in him, Pitt, and around four other stars has “never subsided”.

He said the interest was so intense he would avoid going to the hospital for things you would usually seek medical attention for.

“I have a goal of trying to protect, I don’t want pictures of my kids. We deal in very serious subject matters, with very serious bad guys, and we don’t want to have photos of our kids out there”, he said.

“So we have to work hard at trying to stay private, and it’s tricky, as you can imagine. There’s times you will avoid going to the hospital with something that you would normally go to the hospital for.”

He added: “You will assess how bad something is before you go.”

The actors, who are both in their sixties, also discussed ageing.

Clooney said he told his wife, Amal Clooney, “it doesn’t matter how many granola bars I eat. In 20 years, I’m 80”, adding: “That’s a real number where your bones are brittle and your muscle mass is gone. So s--- changes.”

The actor was one of several key Democrat figures to call on Joe Biden, 81, to drop out of the presidential race.

Clooney also described how he was a “little irritated” by Quentin Tarrantino for refusing to describe him as a “movie star” in a recent interview.

“He literally said something like, ‘Name me a movie since the millennium.’ And I was like, ‘Since the millennium? That’s kind of my whole f------ career.’”

He added: “So now I’m like, ‘all right, dude, f--- off’. I don’t mind giving him s---. He gave me s---.”

In a wide-ranging interview, Pitt also revealed he was attacked by Alcoholics Anonymous for speaking publicly about attending meetings.

Pitt said the group “came down on me” for talking about his experience.”

They were like, ‘It’s anonymous.’ I was like, ‘Well yeah, but if I want to…’”