Andy Richardson: Ghostwriting is almost like acting

The superstar footballer Zlatan Ibrahimovic spent 100 hours with writer David Lagercrantz while working on his autobiography, I am Zlatan.

The two became good friends, as any men who spent 100 hours together must. And then Lagercrantz did what all good ghostwriters do: he ditched Zlatan's verbatim quotes and made a bunch of stuff up. Paradoxically, the stuff he made up was 'more Zlatan' than Zlatan himself.

Zlatan, though initially confused, grew to love it. The book became a huge smash and the fact that the words purporting to be Ibrahmovic's were actually written by a fella called Lagercrantz seemed to trouble no one.

I've never met Zlatan. But I've spent more hours than I care to remember being other people: mostly actors, chefs, musicians and sportsmen, since you ask.

My job is to become them, for a little. To write well, I have to think like they think, do what they do and like what they like. In one extreme case, I even ended up taking a trip to A&E, just like the guy I was writing for, having smashed my foot on hard steel – just like he had. But more of that later.

Ghostwriting is almost like acting: it's like Daniel Day Lewis becoming Abraham Lincoln, Heath Ledger becoming The Joker or Robert De Niro becoming Vito Corleone. You don't have to wear the make-up or the funny clothes, but mentally, you have to become your subject.

I became so immersed in the process that I studied it for a while, signing up at a local university and synthesising theories about high-falutin' epistemologies like emotional labour. I learned about academics and theorists like Arlie Hochschild and Konstantin Stanislavsky and came up with a new theory about my work. And then I got off my high horse and carried on doing what I do best: writing.

There's an inviolate law among the band of brothers who ghostwrite and it is this: you never identify the subjects for whom you've written. Breaching that trust is like telling your one-year-old son that Father Christmas doesn't exist: it's generally considered a bad idea. It's fair game, however, to talk in more general terms: no names, no pack drill – you get the picture. There are some episodes that are simply too personal to recount. Some glimpses behind the curtain will end up going to the grave. People share their innermost thoughts and give you an Access All Areas pass. And that's to be respected – forever.

But other stuff is just plain funny and it bears repeating. Like the guy who was a regular on daytime TV but wasn't really up to much in the 'ideas' and 'words' department.He never knew what he'd 'written' until he saw it in print, being more interested in his cheekbones than the thoughts he was supposedly having.

Ghosting for a subject can go to extreme lengths. I wrote for a severely handicapped sportsman – a multiple world-beater, no less – and spent my first day on the job falling down a drain outside his front door. I damaged my foot to such an extent that I quite literally felt his pain.

On other jobs, I learned about the libellous and the defamatory, the stories of household names who cover up their traces and whose misdeeds are legally prohibited from publication. I learn about the A-listers who get into dust-ups, take too many drugs and sack their staff – but not before they've punched them in the face.

And then, like Lagercrantz, I disappear into the shadows, as though I never existed.