A new book titled 'How to Save a Life: The Inside Story of Grey’s Anatomy' by Lynette Rice will deep dive into the history of the titular hit medical drama. There were many comings and goings throughout the sixteen-year history of the show. But none are more famous that the exit of Patrick Dempsey from the series.

Patrick Dempsey, of course, played Derek Shepherd on 'Grey's Anatomy', aka McDreamy.

THR shared an extract from 'How to Save a Life' in which the reasons for his departure are analysed.

Exec producer James D. Parriott, who was brought back to the series to oversee Dempsey’s exit, says: "Shonda needed an OG to come in as sort of a showrunner for fourteen episodes. There were HR issues. It wasn’t sexual in any way. He sort of was terrorizing the set. Some cast members had all sorts of PTSD with him.

"He had this hold on the set where he knew he could stop production and scare people. The network and studio came down and we had sessions with them. I think he was just done with the show. He didn’t like the inconvenience of coming in every day and working. He and Shonda were at each other’s throats."

'Grey's' writer and producer Jeannine Renshaw detailed how Patrick Dempsey was frustrating the cast, and particularly Ellen Pompeo, by showing up late and not showing that much care.

She says: "There were times where Ellen was frustrated with Patrick and she would get angry that he wasn’t working as much. She was very big on having things be fair. She just didn’t like that Patrick would complain that “I’m here too late” or “I’ve been here too long” when she had twice as many scenes in the episode as he did. When I brought it up to Patrick, I would say, “Look around you. These people have been here since six thirty a.m.” He would go, “Oh, yeah.” He would get it.

"It’s just that actors tend to see things from their own perspective. He’s like a kid. He’s so high energy and would go, “What’s happening next?” He literally goes out of his skin, sitting and waiting. He wants to be out driving his race car or doing something fun. He’s the kid in class who wants to go to recess."

Patrick Dempsey defended himself also, explaining that he was sick of the work and just wanted his freedom back. He says: "It’s ten months, fifteen hours a day. You never know your schedule, so your kid asks you, “What are you doing on Monday?” And you go, “I don’t know,” because I don’t know my schedule.

"Doing that for eleven years is challenging. But you have to be grateful, because you’re well compensated, so you can’t really complain because you don’t really have a right. You don’t have control over your schedule."

A longtime crew member adds: "Poor Patrick. I’m not defending his schtick. I like him, but he was the Lone Ranger. All of these actresses were getting all this power.

"All the rogue actresses would go running to Shonda and say, “Hey, Patrick’s doing this. Patrick’s late for work. He’s a nightmare.” He was just shut out in the cold. His behavior wasn’t the greatest, but he had nowhere to go. He was so miserable. He had no one to talk to."

Dempsey left a final reflection saying: "I very quietly left. It was beautiful. It was raining, which was really touching. I got in my Panamera, got in rush-hour traffic, and two hours later I was home."

Read the book extract here.