If anyone is in any doubt that Prince Harry has read his own ghostwritten 416-page memoir, look no further. For the full Spare experience, only the audiobook will do.

For 15 hours and 37 minutes last week, the Duke of Sussex was in my head. Actually, it was closer to 12. Harry’s voice is so slow, and broken by pregnant pauses and chapter breaks, that despite the pace of the revelations, listening to it at anything less than 1.3x speed felt like my life was being lengthened in front of my ears. And at that speed, weirdly, he sounds eerily like Gordon Ramsay.

We rarely hear royals speak. Since King George V made the first royal radio broadcast 99 years ago to open the British Empire Exhibition, the royal voice has been doled out sparingly. A Christmas speech here, a few choice words at the opening of a garden center there.

Which is why it feels slightly surreal, almost perverse, to listen to Prince Harry — the King’s flesh and blood — narrate his audiobook “in his own words”. And there are many words, not least “penis”, which is uttered eight times. His audio account of applying Elizabeth Arden Eight Hour Cream to his genitalia has already become the stuff of social media meme.

We are used to hearing royals sing in church, their voices drowned out by packed congregations. But Harry has upstaged them all, becoming the first member of the family to perform a solo in an audiobook: an off-key rendition of “Your Song” by Elton John, as sung at the memorial concert for Diana, Princess of Wales, in 2007.

“I hope you don’t mind / I hope you don’t mind / That I put down in words / How wonderful life is while you’re in the world,” he croons. At least we were spared “Candle in the Wind.”

Harry’s use of accents is unpredictable. He may be talking about combat training in the Yorkshire Dales, but a flick of American sends us into the world of Top Gun: “Good morning, this is dude zero one and dude zero two …” Later, in Paris, when he asks his Irish driver to take him through the tunnel where his mother was killed, we get a “what the feck?” in response.

Prince Harry’s voice is so slow, and broken by pregnant pauses and chapter breaks … listening to it at anything less than 1.3x speed felt like my life was being lengthened in front of my ears.

Few listeners will forget Harry’s Ali G impression, delivered to the Queen Mother at a family get-together. “With every repetition of that word, ‘booyakasha’, she’d shriek, which would make everyone else smile.” We are there, cringing in the corner of the room — strangely unable to stop listening.

Partying with the prince in his wilderness years is a Proustian attack on the senses. We meet Will Arnett, the voice actor behind The Lego Batman Movie, and are treated to a “hello Harry” in “perfect gravelly Batmanese” — all before the magic mushrooms come out.

Harry then recounts a conversation with a bathroom pedal bin. “I stared at the bin, it stared back … then it became a head … it said, ‘Aaaaaaaaaah.’” Only we listeners can know what that truly sounds like.

Seasoned audiobook listeners will know that the success of any volume hinges on the caliber of its reader. Financially, Harry is onto a winner: the global audiobook market is huge, set to reach almost $20 billion by 2028, growing at about 26 percent a year.

Although download figures for Spare have yet to be released, about 750,000 copies were sold in the UK across all formats in its first week, of which 467,000 were physical copies — suggesting there were nearly 300,000 e-book and audiobook downloads. Harry has surely joined the pantheon of the kings and queens of the spoken word (lately including Michelle Obama, Stephen Fry and Miriam Margolyes).

Audiobooks are also the natural format for someone averse to others twisting his words. It is harder not to feel empathy when he describes traumatic moments in his life, or side with him in arguments with his brother, when we hear them straight from the prince’s mouth.

The peculiar power of audiobooks means that after 15 hours, listeners may find themselves forgiving the book’s inaccuracies — or forgetting that the words have been heavily polished by a ghostwriter.

“I’m not really big on books,” Harry admitted when he and Meghan started dating — yet he has since said that he has enough material for a second.

Next time, Harry, spare us the seal impressions.

The audiobook of Spare, read by Prince Harry, the Duke of Sussex, is out now from Random House Audio

Tom Calver is the data editor for The Times and The Sunday Times