Secret pad is Letterman's top den

Keeps 'off-limits' office at the Bed Sullivan Theater

By SUSANNAH CAHALAN, JAMES FANELLI and ANGELA MONTEFINISE

Last Updated: 9:34 AM, October 4, 2009

Posted: 3:15 AM, October 4, 2009

Lights, cameras and plenty of action!

Skirt-chasing funnyman David Letterman's restricted office at his Midtown studio has all the trimmings for a bachelor on the prowl, including a fold-out couch and a kitchen, The Post has learned.

The randy comic, who was the victim of an extortion attempt over his in-house dalliances, keeps the quarters private to all but a select few staffers, sources said.

"It's off limits to pretty much everybody," a "Late Show" insider told The Post yesterday.

Letterman is known to come and go from the crash pad at all hours, the source said.

"If he is having an affair or fooling around with somebody at work, she wouldn't be noticed coming in or out, or seen as something strange because she works there," the source said.

Located in the cavernous Ed Sullivan Theater, Letterman's office comes with a reception area as well, a source said.

A spokesman for Letterman's production company, Worldwide Pants, denied that the digs are a love nest.

A source close to Letterman said the host simply crashes on the fold-out couch on Mondays, when he drives from his weekend home in North Salem, Westchester County, to the Broadway studio at 2 or 3 a.m.

Letterman stays at his TriBeCa apartment during the rest of the filming week, but he is also known among staff as a night owl and for keeping odd hours at his office.

While the show usually wraps by 7 p.m., sometimes he stays and watches the broadcast of his show in his office at night, an insider said.

"He doesn't work regular hours," the Letterman source said. "It's not a 9-to-5 place."

CBS bought the Ed Sullivan Theater for $4 million after inking a deal to bring Letterman over from NBC to the Tiffany Network in 1993, according to reports at the time. Additionally, the studio spent more than $4 million to rehab the storied venue.

Like he does with his hyper-secure office space, Letterman keeps his personal life under lock and key.

But that veil of privacy was lifted Thursday night, when he told viewers that he was the victim of a $2 million extortion plot and admitted on-air to sleeping with staff members.

"48 Hours Mystery" producer Robert "Joe" Halderman, 51, has been arrested for the alleged blackmail.

Manhattan prosecutors say Halderman threatened to publicly reveal Letterman's trysts.

Letterman's former personal assistant, Stephanie Birkitt, 34 -- Halderman's live-in girlfriend until last month -- has been identified by sources as one of the paramours.

He allegedly attempted to shake down Letterman with a tell-all screenplay, along with salacious e-mails between the comic and Birkitt, and a secret sex diary the woman kept in their Norwalk, Conn., home.

At her parents' home in Plymouth, NH, yesterday, Birkitt's father, Steven, said his daughter was dealing with the issue.

When asked if she was OK, he said, "I guess."

"It's a tough time, that's really all I can say," he added.

Halderman, a divorcée who was struggling with mounting debt and high monthly alimony payments, was released on a $200,000 bond Friday after pleading not guilty to attempted grand larceny.

Prosecutors continued to build their case against him Friday night as they executed a search warrant at his CBS office. Law-enforcement officials were looking for original copies of the blackmail evidence.

Halderman declined to comment yesterday at his Norwalk home. He was later spotted running errands at a bank and dry cleaners in the morning before holing up in his home.

Letterman was once again skewered on Saturday Night Live last night, a day after Jay Leno and Jimmy Fallon took their pot shots at him. Staffer Seth Myers joked that after sex, the "Late Show" host would say, "Stay tuned for Craig Ferguson."

Additional reporting by Erin Calabrese, Kathianne Boniello, Murray Weiss and Bill Gallagher

scahalan@nypost.com

@ BED SULLIVAN THEATER