Mr Craker, who was with the princes at Balmoral when Princess Diana died, said in an interview he was in “disbelief” when he found about her death.
Reflecting on the funeral in 2017 documentary Diana: The Day We Said Goodbye, he said: “Most of the time it was almost as if it was raining flowers. It was very poignant knowing that each of those flowers represents the emotions of somebody in the crowd.
“We tried using the windscreen wipers but the driver was finding it quite hard to see.
“I called the motorcycle escort in front and said we need to stop. I took the flowers off the bonnet and laid them beside the road.”
In an interview with the New York Post, he added: “I was standing at the rear of the hearse and William looked up and acknowledged me.
“I looked towards him and nodded. William was comforted that I was with his mum on her final journey.”