Come Oscar night and most people in the industry are focused on the stars they hope to see walk on stage and pick up a statuette. But for Robert Mann, John Lane and Dennis Bridwell, the heads of three leading Los Angeles-based personal-protection agencies, February 27 will be a worry.

Sitting in the shadows - as close to their clients as the Academy of Motion Picture Arts and Sciences protocols will allow - they won't care who flashes a winner's smile, just so long as nobody gets shot in the process, or stabbed, or followed home.

"We're paid to be paranoid," says Robert Mann, sitting in his fifth-floor office with its sweeping view of Sunset Boulevard. Until recently Mann was paid to be paranoid for Ashley and Mary-Kate Olsen, his firm, Worldwide Intelligence Network (WIN), providing bodyguards and anti-stalking intelligence to the celebrity twins around the clock.

"This time of year there's a marked increase in demand for bodyguard services," he says, "and events like awards ceremonies and premieres present particular challenges."

Mann, who also has Rod Stewart and Sylvester Stallone among his clients, started out in special operations, working for a government intelligence agency (he's a little coy about using the well-known initials), "blending in, keeping my eyes and ears open".

It was in special ops that he honed his investigative skills, and sharpened his appetite for situations that most people would pay to avoid, such as going into LA's notoriously dicey South Central district last year to doorstep a mysterious someone who had been impersonating Mary-Kate in an internet chatroom in order to set up meetings with young girls.

The mother of one of these girls contacted Mary-Kate's theatrical agents and the agents called Mann. "I had to shut this guy down quick," he says. "Who knew what the hell he was planning once he got the girl where he wanted her?"

After sifting through internet traffic for a week, he finally traced the impersonator to a physical address. "I was armed and had a 300-pound [136kg] ex-football player with me, but I still didn't know what was behind that door when I knocked."

As it turned out the impersonator was a young gay man, and the only threat of violence came from the abusive father furious with his son. But it could have been otherwise. Like the time Mann traced a stalker to his house.

"The guy had got into the twins' place of business and scared the hell out of the staff," he says. He ended up face-to-face in the street with a character who was obviously not fully in control of himself.

"I said what he'd been doing had to stop," Mann recalls, "told him the cops would be patrolling his house on a regular basis." Mann's departing line was pure Terminator. "I told the guy I was his worst nightmare." The stalking stopped.

WIN's promotional literature says its agents are "trained and experienced in the avoidance of confrontation", but there's a gun on the wall in Mann's office wired to a plaque that says: "We don't call 911." In other words, don't worry about getting involved in embarrassing litigation, or having to appear in court with the person who's been making your life a misery; we'll deal with the problem.