In his highly anticipated autobiography, Spare, Prince Harry describes how his sadness over the death of his mother, Diana, Princess of Wales, led him to seek help from a woman who “claimed to have ‘powers’” and to be able to relay a message.

“You’re living the life she couldn’t,” Harry says the woman told him. “You’re living the life she wanted for you.”

Diana was killed in a car crash in Paris in 1997, when Harry was 12.

Now 38, Harry will publish Spare next week. Amid reports of highly restrictive security around the release of the book, the Guardian obtained a copy.

The description of the visit to the woman – about whom Harry does not use words like “psychic” or “medium” – comes late in the 400-page book, amid the prince’s account of his marriage to Meghan Markle, an American actor, and troubled relations with the royal family including what he says was a physical attack against him by his brother, Prince William.

Harry writes about his mother and his grief throughout his book, at one point describing repeated drives through the tunnel in Paris in which she died, in an attempt to understand what happened.

His account of what he says was a conversation with his dead mother is short. Harry, who now lives in Los Angeles, does not say where the meeting happened, or when. He does not name the woman involved.

The prince says he “recognised the high-percentage chance of humbuggery” but went to meet the woman because trusted friends recommended her.

“The minute we sat down together,” he writes, “I felt an energy around her.”

The prince says the woman told him she felt an energy around him too, and said: “Your mother is with you.”

Harry replied: “I know. I’ve felt that of late.”

The woman, he writes, told him his mother was with him “right now”. Harry says his neck grew warm and his eyes watered.

The woman told Harry his mother knew he was “looking for clarity” and “feels your confusion”, and knew he had “so many questions”, and said answers would come in time.

The prince also says the woman told him Diana said: “You’re living the life she couldn’t. You’re living the life she wanted for you.”

Harry, who in his book also describes endless clashes with the press amid trips to London clubs and visits to Africa, Europe and Hollywood, and admits to regular drinking and drug-taking, says he wanted to believe the woman but needed “proof. A sign. Anything.”

One such sign offered by the woman involved a story about an ornament, and a claim that his mother knew about it because “she was there”.

Earlier in the book, Harry recounts how a Christmas tree ornament in the shape of his grandmother, Queen Elizabeth II, was accidentally smashed by his son, Archie.

The woman, he writes, repeated that his mother was there when the incident happened, saying: “Your mother says … something about a Christmas ornament? Of a mother? Or a grandmother? It fell? Broke?”

Harry said: “Archie tried to fix it.”

The woman said: “Your mother says she had a bit of a giggle about that.”

After the Guardian broke the first details of Spare on Wednesday night, the book briefly appeared for sale in Spain, leading to other news outlets obtaining copies.

Spare by Prince Harry, The Duke of Sussex (Transworld, £28). To support The Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.