American cowboy pal confided in Queen Elizabeth over 'guilty conscience'.

For over three decades, Queen Elizabeth II maintained a close friendship with an American cowboy.

The documentary "The Cowboy and the Queen" examines the surprising friendship between the British monarch and Monty Roberts, a horse trainer from California, and how Roberts' training techniques were adopted in the U.K. with the queen's support.

In 2022, at the age of 96, England's longest-reigning monarch passed away. Roberts received an invitation to attend her funeral at St. George's Chapel in Windsor Castle.

"My wife and I have been married for 68 years, but horses are my second love," Roberts said in an interview with Planet Chronicle Digital. "… "Her majesty and I shared a deep love for horses. And getting to know her was such a wonderful time in my life."

As a teenager, Roberts developed a revolutionary method for training horses humanely, which involved teaching juvenile or wild horses to accept a saddle and rider without suffering the violence of being "broken." This approach earned him the nickname "horse whisperer," and was widely reported on by the UK Times.

And in 1989, he caught the queen’s attention.

"Roberts clarified that he had a strict focus on horses and did not delve into human affairs at the time. Later, racehorse trainers in California approached him, stating, "This is the way we must proceed. What we do with all the whippings, restraints, and front-foot roping is not as effective as this method.""

WATCH: QUEEN ELIZABETH'S UNEXPECTED BOND WITH AN AMERICAN COWBOY REVEALED

"We hosted three or four open houses for California racehorse trainers, and magazine writers came to observe. They wrote about their experiences, which the queen read in the magazines. The queen was fascinated by the concept of nonviolent training."

The queen, intrigued by Roberts' methods, passed on the articles to her horse manager. Despite dismissing Roberts' techniques as "hogwash," the manager was tasked with observing Roberts in California to determine his authenticity.

"Roberts stated, "He came and observed me. He exclaimed, 'I need to see another one, I need to see another one.' I completed approximately four horses for him. He returned to the U.K. and informed her, 'It's genuine.' And she replied, 'I want him here.'""

When Roberts received a call stating that the queen of England wanted to meet him, he initially thought it was a joke. However, it wasn't long before he and his wife Pat flew across the pond to Windsor Castle, where the queen was waiting for him with 23 horses.

"Five days ago, he stated that he would be there."

The Times reported that Roberts employed "gentle encouragement" and "body language" instead of "ropes and whips" during horse training. The traditional method of breaking horses would have required four to six weeks.

Roberts claimed that the queen walked toward him "in a daze."

"He claimed, "She said, 'I have such a guilty conscience,' and 'I should have told my father I wanted to learn nonviolent ways to train horses. And now I know it’s possible.'""

From that point onward, we became close friends due to our shared love for horses.

The young princess was repeatedly told, "It has to be done," as she tried to hide from seeing horses being broken "the old-fashioned way" when she learned to ride at the age of 6.

"She said, ‘I have such a guilty conscience. I should have told my father I wanted to… [learn] nonviolent ways to train horses. And now I know it’s possible.’" — Monty Roberts, horse trainer and Queen Elizabeth II's friend

"Roberts stated, "She was told all her life, 'It has to be done,'" and then added, "Can you imagine in 1989 when she was in her 70s, me coming in and saying, 'It doesn't have to be done that way?' From that moment forward, not one horse was ever struck that belonged to her... And if you [struck] a horse, you need another job.""

Despite criticism of her friendship with Roberts and his teachings, the queen remained unfazed and invited him to demonstrate his methods to family members and skeptical palace aides.

The queen helped spread Roberts' teachings worldwide and saved his career by introducing him to horse breeders, traditional trainers, and other equine advisers, finding him a publisher, and encouraging him to write his bestselling book, "The Man Who Listens to Horses."

"Roberts stated, "She invited me to visit places that I can't describe, which were small cottages hidden in the woods of different locations. She and Prince Philip would go there with the dogs accompanying them.""

The queen honored Roberts by placing sculptures made by his wife on private properties and later named one of her prized corgis after him. In 2012, Monty the dog appeared in a James Bond sketch for the Olympics opening ceremony alongside the queen and Daniel Craig as 007.

The UK Times reported that Roberts was appointed a Member of the Victorian Order and the queen became a patron of his charity, Join-Up International, which teaches gentle horse training and supports military veterans and first responders with PTSD.

Boris Johnson, the former British Prime Minister, stated in his memoir that the queen had bone cancer before her passing. He claimed that the monarch's frequent phone calls with him ended after her diagnosis, and all communication had to go through her doctors due to her pain.

Today, Roberts likes to remember happier moments with his friend.

"The queen called me while we were on our way, saying that Princess Margaret was with her and her sister, and wanted our entire team to visit Windsor Castle," he remembered. "You'll demonstrate how you arrived as a cowboy."

As he approached Windsor Castle, Roberts recalled the queen's speech with Princess Margaret outside the round pen. The younger sibling was terrified that the horses would break free and harm her.

"Roberts stated, "I would remove my cowboy hat every time the queen asked me a question, as Princess Margaret had been asking me.""

The fourth time she visited, she stated, "Monty, it's not necessary for men to remove their hats when conversing with the queen." I responded, "I believed you did, Your Majesty. It makes sense to me that one must take off their hat when speaking to the queen. What do you mean I don't have to remove it?"

"If you're wearing a uniform, you don't have to remove your hat. The men guarding me around this building are all in uniform and you can speak to any of them without them taking off their hats because they are in uniform."

"I looked down at myself and said, 'This is how I dress,'" Roberts continued. "The queen tapped me on the shoulder and said, 'I dub this your uniform.' I never saw her again without these clothes on... I'm still in uniform."