James Marsters was in "personal hell" shooting 'Buffy the Vampire Slayer's "problematic" sexual assault scene

He admitted on the 'Inside of You' podcast: "It's the darkest professional day of my life.

"It's a problematic scene for a lot of people who like the show."

Of his neck pain, he added: "I just collapsed to the floor. I'm like, 'I guess I'm kind of tense right now,' you know?

"We got the scene in the can, and it was - it was hell. I was in personal hell."

The actor explained the scene was inspired by a "painful" experience one of the show's writers had had in college when she tried to reconcile with an ex.

He said: "She had gotten broken up with and she went to her ex's place and thought that if they made love one more time, everything would be fixed.

"And she kind of forced herself and he had to physically remove her from the premises. And that was just like one of the most painful memories of that time of her life.

"[The writers] thought that since Buffy was a superhero, that they could flip the sexes since Buffy could defend herself very, very easily from this. They thought that they could have a man do it to a woman and it would be the same thing, I think."

But James argued against the scene because he felt it would be upsetting for viewers.

He recalled: "I said, 'You know, guys, we're providing a vicarious experience for the audience.

"And so I was saying, 'You know, everyone who's watching Buffy is Buffy, and they're not superheroes. So, I'm doing this to every member of the audience, and they're gonna have a very different reaction.' "

And he insisted he didn't care about how the scene would change fans' opinions of his character.

He said: "I wasn't thinking of that. I was just having to do that to Sarah. You know, I was just having to live through that reality."

The 'Smallville' actor refuses to be involved in projects featuring similar material.

He admitted: "I don't like sexual predation scenes. Anything that has that to do with it, I don't audition for those things.

"If there's a movie with that kind of material, I don't go to see the movie. If it pops up on television, I've got to turn the television off before I break it.

"I have a very visceral reaction to that stuff."