WARNING: This story details of sexual assault and may be triggering

A British comedian has revealed he was raped while on tour in New Zealand, and how it took him 10 years to tell anyone about it following the trauma the attack had on him.

In a new book about how he left a career in medicine for comedy and writing, Adam Kay explained how he thought an opportunity to do a 20-minute set in New Zealand would be the launching pad into a comedy career.

Kay said he was also planning on using the trip to cheat on his wife, with a man, before returning to her and a heterosexual life.

In his book, he said detailed how he planned to engage in his sexual endeavour while keeping a low profile.

A sauna "sounded like probably the most appealing/least appalling option and the best chance of ­getting what I wanted pronto and incognito," he wrote.

Instead, Kay was raped by a man who he thought was escorting him to the sauna. The attack left him traumatised for over a decade.

Speaking about the horrific ordeal, Kay said he gave a false name and put on a French accent at the entrance. But his day took a sudden turn.

"A man in his 40s stood up, took my arm and wordlessly led me to a dimly lit cubicle, where he raped me," and then said "thanks" afterwards.

For years Kay wrestled with the feeling of guilt and blame, and even questioned if he had done something wrong himself.

Kay explained he likes to give people the benefit of the doubt and later tried "to work out if there could have been some kind of ­misunderstanding, something I did wrong".

But he has no doubt he was raped.

"But I can't – the truth of it is inescapable. I was clear. I said no when it became obvious he wanted this interaction to go a lot further than I did," he wrote.

"I said no, again, when he started. I said no when he ­overpowered me and pushed my head into a wipe-clean cushion that stank of anti­septic."

Kay tried to scream, but knew there was no chance he would be heard.

"Not by this man who didn't want to hear and not by anyone else, thanks to the rhythmical pounding of the music".

The rapist then said "thanks" before leaving.

"Thanks. You don't say thanks to someone you've just raped, do you? Was coming here in the first place my consent?" Kay wrote.

"Not pulling my hand away when he took my arm – was that a way of saying yes, in a language I'd never been taught, negating everything I would say afterwards?"

Adam Kay is pictured at the National Book Awards on November 20, 2018 in London, England. Photo / Getty Images

Kay never went to the police, saying it was unthinkable, believing the case would be flimsy.

"Saying it out loud would make it real; I would never be able to deny it or pretend it never ­happened, which already felt like my only way of getting through it," he wrote.

He thought the police's response would be "you can't get raped if you go somewhere looking specifically for sex".

For a decade he told no one about what happened to him. "Maybe I was too ashamed."

"Or maybe I just knew from the moment it happened that I would never forget it: every minute, every second, etched into me in indelible ink, would be with me forever."