Marc Laidlaw, the esteemed sci-fi writer who has worked at Half-Life developer Valve since 1997, has confirmed his retirement from the Bellevue, Washington studio.

He was the sole writer for both Half-Life 1 and 2, and had crafted each game's wider narrative. Later, he was assigned as lead writer on Half-Life 2 Episode 1 and 2.

It is not clear if Laidlaw finished the plot for Half-Life 3 before leaving Valve. The status of that project remains a closely guarded secret, with Valve remaining silent on its progress since the release of Half-Life 2: Episode 2 in 2007. In the past several years, fans have begun to raise questions of whether the project is in development at all.

In an email exchange between Laidlaw and a fan, the author explained he had retired mainly for personal reasons, and appeared to suggest his departure was perfectly amicable.

"I am no longer a full or part time Valve employee, no longer involved in day-to-day decisions or operations, no longer a spokesperson for the company, no longer privy to most types of confidential information, no longer working on Valve games in any capacity," he said.

"An outwardly obvious reason is that I'm old, or anyway oldish. My nickname when I first started at Valve in 1997 was 'old man Laidlaw'. The little baby level designer who gave me that that nickname is now older than I was then.

"I had a good run but lately I have been feeling a need for a break from the collaborative chaos of game production, and a return to more self-directed writing projects."

Laidlaw said his ambition is to return to writing in mediums other than games, but appears to be open-minded about returning to Valve to write in a freelance capacity.

He said: "It feels like the time is right to return to my roots and see where that takes me. It might well take me back into games by other routes, but certainly that's not part of the plan.

"My friends know they can consult me if questions come up that I can help them answer."

Other notable writers at Valve include Chet Faliszek and Erik Wolpaw.

"Where Valve may choose to take Half-Life in the future is not in my hands," Laidlaw said.

"I have been a grateful co-creator, but my time working on the series is behind me."