THIS week saw the news that Prince Harry has signed a book deal with Penguin Random House to publish a memoir next autumn.

The book, according to the blurb, is written ‘not as the prince I was born but as the man I have become'.

Depending on which account you read, the deal was worth anything between £18 and £29 million and was for between one and four volumes.

Plenty has been written about the shoulds and shouldn’ts of publication. Of more interest to me was that the book would be penned by JR Moehringer, an American ghostwriter best known for his work on Andre Agassi’s memoir, Open.

Back when I was a commissioning editor, I tried and failed to buy that book: Agassi’s life was the sort of rollercoaster ride that is publishing golddust. With Moehringer on board, the book was frank and open, rather than the usual anodyne sports autobiography.

I was interested, too, because I’ve been a ghostwriter myself for the last decade. Over that time, I’ve written getting on for 20 books, including memoirs by politicians, rock stars, footballers, soldiers, sporting world champions and reality TV stars.

Usually, I sign some sort of non-disclosure agreement, but even when I don’t the job is one of discretion. I don’t publicly discuss who I’ve worked with.

Last week, I had an email from a fan of one of the people I’d written for, who’d worked out that I was the ghost.

I was incredibly fortunate, she told me, to have spent time in this person’s company. She’s right: it is a strange, fascinating and privileged position to be in.

Each book varies, but normally involves a long series of interviews – in my case, usually around 40-50 hours spaced out over a couple of months.

That’s a long time to be sat down talking to someone, and I usually have an initial meeting to see if we’re going to get on (I remember one meeting with a famous cricketer who gave one-word answers to all my questions, and knew it wasn’t one for me).

With the right person, however, the conversations can be extremely revealing. For some, the process can almost feel like therapy, and I’ve had people talk about abuse, affairs and tragedies they’ve never previously opened up about. Sometimes these stories end up in the book: at others, I protectively keep the secrets between us.

For Prince Harry’s memoir, that process will be important. If recent interviews are to go by, he will be happy to unload. Good ghostwriting, though, is not just about extracting the juice, but applying judiciousness as well.