Brian Baumgartner explains fascinating reason The Office US was split into two rooms

The Office US star Brian Baumgartner has explained the practical reason why some of the cast members seated in a separate room.

It's now over a decade since the final episode of The Office US graced our screens, seeing the other will they/won't they couple Dwight (Rainn Wilson) and Angela (Angela Kinsey) tie the knot at Schrute Farms, complete with an emotional reunion between the Dunder Mifflin employees and their former boss Michael Scott (Steve Carell).

It was a perfect full-circle moment for one of the most popular sitcoms, however, there are still plenty of mysteries from The Office which still prevail.

Did you know this behind-the-scenes fact about The Office? (NBC)

Who was the infamous 'Scranton strangler', why did Michael hate Toby (Paul Lieberstein) so much and who were the unnamed extras walking around the office in season one?

While we may never get the answers to some of these questions, actor Brian Baumgartner, who played numbers-challenged accountant Kevin Malone, has cleared up the reason why the set featured a main office and secondary annex.

And the reason may actually surprise you.

While the show depicts sitting in the annex as a 'lesser position' in the office, Baumgartner revealed the very practical real reason during a recent podcast interview.

Appearing on an episode of Joe Vulpis' Lightweights Podcast earlier this month, the actor explained the fun 'easter egg' behind the seating arrangements and how it related to the cast's roles behind the scenes.

Toby Flenderson (Paul Lieberstein) was one of the main occupants of the annex (NBC)

Think about who primarily sat in the annex, Toby (Lieberstein), Kelly (Mindy Kaling) and, in later seasons, Ryan (BJ Novak), all of them actors who were also involved in the writing of the show.

"There was the main office... and then there was the other side," he began. "If your desk was in the annex, you were a writer."

Going on to explain the reason for this decision, Baumgartner continued: "They did this because the camera was always moving around. We were there all the time.

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"So Greg (Daniels, director and showrunner) needed the writers in the writers room sometimes." This meant the seating arrangement allowed for Lieberstein, Kaling and Novak were able to be head up to the writers room when needed without ruining continuity while filming.

"I did not know that," host Vulpis replied. "Fun fact."

Baumgartner isn't the only Office alum to reflect on the show's unique relationship between writers and actors, with Jenna Fischer revealing in her book The Office BFFs: Tales of The Office from Two Best Friends Who Were There how having writers double up as actors was a deliberate decision by Daniels to 'change the structure of how a traditional sitcom operated'.