WWW- Princess Diana’s former butler says in his new book that the depth of her capacity for compassion only surprised him once.

That was when, according to Paul Burrell’s second memoir of his time with the princes, “The Way We Were,” Diana asked him to help her by burying the stillborn child of a friend, Rosa Monckton, on the grounds of Kensington Palace.

The story may only add to the storm that Burrell has raised in the British press with his portrayal of himself as the only person standing up to defend the late princess’ reputation, and his criticism of the royal family — including Princes William and Harry, who he said have not done enough to defend their mother’s memory in the nine years since her death.

While the story of the secret burial might scandalize some who feel it was improper for a child’s grave to be dug on the grounds of the royal palace, Burrell wrote that for him the act was just one more proof of the nobility of the woman he called “the boss.”

“I have thought long and hard about whether to tell this story,” Burrell writes in the book, which is to be published by Harper Collins on Sept. 12. “But what I witnessed was the ultimate act of compassion and friendship, which I think reflects greatly on the boss and sums up her humanity. Acts of kindness don’t get much bigger than this.”

According to Burrell’s book, Diana told him that if anyone asked him what he and fellow butler Harold Brown were doing digging a five-foot deep hole in the palace’s backyard, they should say that friends of Diana’s were burying a pet.

Diana even helped with the digging, after she came out and found him with blistered hands and covered with mud, Burrell wrote.

“‘Let me help,’ she said, and jumped in and took the spade, as I climbed out. She put her back into, for about ten spades’ worth of soil tossed on to the bank — she wanted to do her bit,” he wrote.

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“That evening, the princess examined it with me,” Burrell wrote. “She stood in silence, staring into it, lost in her thoughts. When she looked up, her eyes were brimming with tears, but she smiled in the knowledge that everything had gone to plan. In those few quiet moments in the garden, I sensed how important this task was to her.”

There was a small ceremony, with just six people around the grave, and after the child’s parents left, Diana and Burrell returned to fill in the grave, he wrote.

It was then that she told him, according to the book, “The only problem … is that people will find this baby one day and say it was mine.”

“She spoke it as though it was a sad inevitability, one more aspect of her life that would be misunderstood,” Burrell wrote. “Perhaps that is another reason why this story should be told.”

The book by the late princess’ confidant and friend includes his own photographs of her inner sanctum in Kensington Palace — her sitting room, her private dressing room, even the collection of teddy bears in her bedroom — along with an intimate account of Diana’s private life, including her secret and not-so-secret loves.

Some of Burrell’s comments on his publicity tour for the book — including statements made to ABC News’ Kate Snow in an exclusive interview broadcast on “Good Morning America” — have brought him under fire in the British media.