British security will be on high alert on Prince William and Kate Middleton's wedding day, and ET gets an exclusive look at the top-secret facility that's responsible for it all.
Chris Jacobs met with operations manager Daniel Brown to talk about security leading up to and on the big day. The undisclosed compound, located deep beneath London, contains over 100 cameras that constantly survey roughly half of the Westminster area of the city. With over 5,000 officers, undercover agents and surveillance around the clock, Daniel and his team seem to have everything covered. He even delivers a warning for any troublemakers. "If you are going to be doing anything you shouldn't be, then the cameras will pick you up."
Watch more from our tour of London's best kept secret!