Harry wrote in Spare, “The driver had to keep pulling over so the bodyguard could get out and clear the flowers off the windscreen," per The Telegraph.

“The bodyguard was Graham. Willy and I liked him a lot. We always called him Crackers. We thought that was hysterical,” he added.

Craker previously spoke to the New York Post in 2017 about taking part in the documentary Diana: 7 Days That Shook the Windsors that was released that year.

He told the outlet that Diana's death was, "Difficult to take in. It takes a while to absorb and then you feel the need to make sure what you’re hearing is true — and that didn’t take long to establish. From there on, it’s the policeman’s instinct to assess the situation and carry on."

Craker was with the royal family in Scotland when the late princess died, telling the outlet he wasn't really able to comfort William and Harry. "That was obviously the duty of the parents, family and everybody else they thought could help. When we did meet, it was quite a somber atmosphere," he said.

"Perhaps the most emotional [part of the week following Diana's death] was seeing William the morning after [the car crash]. I saw William walking his dog outside, and I walked up to him and said, 'I’m very, very sorry to hear your bad news.' William very sadly said, 'Thank you.' Not wishing to encroach upon his grief, I then walked on and William continued walking his dog," the New York Post reported.

Craker also told the outlet about traveling in the hearse with Diana's coffin. "I was standing at the rear of the hearse and William looked up and acknowledged me. I looked toward him and nodded. William was comforted that I was with his mum on her final journey," he said.

Craker — who was also a guest at William's wedding to Kate Middleton in 2011 — was previously made a member of the Royal Victorian Order by the late Queen Elizabeth for his services to the royals, The Telegraph noted.

In recent years, Craker spent time working with local organizations such as the Southern Maltings art center in his East Hertfordshire hometown of Ware, per Sky News.

The charity shared a tribute and a photo on Facebook, writing, "While to the most important people in his life Graham was a father, and grandfather, to us he was a valued friend and colleague."

"From a career in the police, as a member of the protection squad, a huge driving force in the rotary and eventually a key volunteer at the Southern Maltings, so many people are going to miss our very own James Bond," the caption continued.

"Our broken hearts go out to his family and everyone who knew him," the April 3 post concluded. "RIP Crackers, we’ll make sure you are remembered behind the bar and will raise a glass for you this evening."

Kensington Palace declined to comment when contacted by PEOPLE. Prince Harry's spokespeople and the Metropolitan Police didn't immediately respond when contacted by PEOPLE for comment.