Located just south of Broadway, the Potbelly Sandwich Shop is always full during the very short lunch period enjoyed by the 2,000 or so employees at the New York field office of the FBI (Federal Bureau of Investigation). And for good reason. The FBI office is just a few metres away from the shop and many of its analysts, investigators and security agents pour into the sandwich shop at lunchtime for a short break or a take-away sandwich or "mac and cheese". Far from the discreet Manhattan haunts where