I assure them that I am not a bad person. I will be asking a lot of weird questions. We are writing a book because we aren't telling a quick story on a chat show.

I always start with "the talk" when I meet potential subjects with a desire to have their story written. I have been doing the job for more than a decade and it bears little resemblance to most peoples assumptions.

People often open up about their worst moments, greatest secrets, biggest fears and what they overcame to overcome them. I feel compelled to witness that and give them the space to talk about their experiences. There is only one way to get to the core of a story.

This requires a cocktail of pastoral care that would look callous to an outsider. It's often those with the most interesting stories who don't know what they're talking about. They were unselfconscious about sharing intimate details when I gave them the talk.

We’re not telling a quick story on a chatshow, we’re writing a book

Others don't give any information at all. They will tell a story of deep trauma, the worst moment in their life, and they will be amused when I ask if I can double check. It's rude. I am fascinated by the lives people have led but also by the colors in which they have remembered those lives and what they think of them. For the first time in her life, she realized how young she'd been when she fell in front of me.

What does this mean for the ghostwriter's mind? I head home on the bus with my head spinning at the things I just heard and an obligation to follow up with a cheery text about deadlines. When it comes to writing memoirs, deadlines are an issue, as they can lead to days on end spent with a subject, only to hear their voice in my head for weeks as I rewrite their lives. My son recognised a person I was working with on TV and started talking to her, so he was familiar with her face on my screen

Slowly becoming part of their life, their family, and their story is what it really means. When a story hits the press, I feel protective of the subjects. I have random celebrity grudges because of stories I was told. I will never work in an industry that I am loyal to. I've been called by subjects in tears in the back of cabs at 1am on Boxing Day and when they have just come round after a nose job.

Most of the time, only a small group of people know I was involved in the book's creation. I was once likened to Harvey Keitel's character in the movie "pulp fiction", who was called "Turn up, request a coffee, get the job done, leave". The most frequently asked question is "how can you bear it?" No one knows you did it.

I was surprised that this is the best part. I would have given up writing my own books by now if it weren't for the help of ghostwriting.

Highs have included genuine friends made and an insight into the lives of close friends. It was a personal low when I thought I had a rat in my kitchen, but it was actually my subject's hair extensions. She lingered in my head all week, so it made sense that she would linger in my kitchen.

I’ve been called at 1am by subjects in tears in the back of a cab

I can't explain how much pleasure I get from my job. I think most people are fascinated by the idea of being hidden. The fairytale of an undiscovered talent doing the hard graft under someone else's name still tantalises, as a Barton Fink-style secretary covertly entertaining the public while a drunk in the corner takes the credit.

It is the possibility of access to the powerful for some. The question of who wrote the memoirs of politicians when they leave SW1A has long been a source of fascination, one only compounded by Robert Harris's political thriller, adapted for screen by Roman Polanski as The Ghost. That and the writing hut by the Prime Minister.

Kate Winslet is set to star in a TV adaptation of the novel Trust, which is about the life of a Wall Street tycoon who hires his own ghostwriter.

The idea that there may be one version of the truth and that it may be kept from the reader is at the center of all this curiosity. The title of the ghost writer doesn't do much to clear this up. Most memoirs I have worked on have involved no cover-ups, but have needed someone with a clear idea of how to tell a story. You may not be a writer if you have a book deal.

It was no secret that Rebecca Farnsworth was the constant hand on the tiller for the glory years of the KATIE PRICE empire. Each of the 14 books written with Price was named after him. Her first book, Being Jordan, sold more than 1m copies in 2005 and led to a veritablyPepys-like series of memoirs about her day-to-day life, alongside novels including Crystal.

The writing process is usually collaborative The initial meeting is usually arranged by agents and feels more intense than anything else. The subject and I are trying to decide if we can spend up to nine months talking to each other. Do they really want me to drink their coffee and ask them what it was like to lose so much?

After years as a ghost, I now feel fully alive

What do you think about my subject? I don't know if their life is interesting to me. I said no to one project because it was going to involve a lot of opinions on vaccines and vitamins, and I found it difficult. I slip into someone else's skin for months at a time, before slithering away again undetected, and at times friends have despaired of how happy I am to do that. They told me that I was losing myself in the lives of other people. If not slipping into the lives of other people for a few months, what is novel writing?

They thought I was wasting my time, but they were wrong. I took refuge for months in the lives of other people because I felt trapped by my own story. I realized I was also learning about living when I thought I was learning about writing. I began to understand more fully how much life there is to be lived and how many ways there are to do it when I wrote about different types of pain, ways of dealing with it, and perception of success.

I made the most of my time here. I have two books out this year, after many years as a ghost. There is a book with my name on it. The other has another person's.

The book is available at guardian bookshop.com.