“Nothing illustrates the Queen’s devotion more than her marking his 90th birthday by bestowing on him one of her own titles, that of Lord High Admiral,” Richard said.
For Philip, who had previously had a promising career in the Navy until he was forced to give it up, the title meant he could relish in some of the honour that comes along with such a title.
Richard added: “Cut adrift for so long from the life at sea he’d loved, it meant he’d been effectively returned to the Senior Service.
“Friends describe him as being ‘almost in tears’ at the gesture,” he wrote. "I thought I was going to have a career in the Navy, but it became obvious there was no hope.
“There was no choice. It just happened. You have to make compromises. That's life. I accepted it. I tried to make the best of it."
The royal revelation comes after Prince Harry and Meghan Markle shocked the world – and the Queen – by announcing they intend to quit the royal family and move to North America.
In a statement issued on their Instagram account with 10.1 million followers on Wednesday evening UK time, they said: "After many months of reflection and internal discussions, we have chosen to make a transition this year in starting to carve out a progressive new role within this institution."
They continued: "We intend to step back as 'senior' members of the Royal Family and work to become financially independent, while continuing to fully support Her Majesty The Queen. It is with your encouragement, particularly over the last few years, that we feel prepared to make this adjustment.
"We now plan to balance our time between the United Kingdom and North America, continuing to honour our duty to The Queen, the Commonwealth, and our patronages. This geographic balance will enable us to raise our son with an appreciation for the royal tradition into which he was born, while also providing our family with the space to focus on the next chapter, including the launch of our new charitable entity,” the statement read.