. >> maybe, even so, billingham says the crowd won't just be made of of spectators. >> there will be armed, responsive units. >> special forces. >> special forces, yeah. >> the threat extends beyond street level, jeff. this week, police announced a 48-hour, no-fly zone over windsor. we were told defenses are in place, to take down any drone flying overhead. >> so interesting to hear some of the details. charlie, thank you. >> cbs news live coverage of the royal wedding begins saturday at 4:00 clock a.m. eastern. that is 3:00 central. 1:00 a.m. in the west. coming up next, how did he get away with it? [thoughtful sigh] still nervous about buying a house? a little. thought i could de-stress with some zen gardening. at least we don't have to worry about homeowners insurance. just call geico. geico helps with homeowners insurance? good to know. been doing it for years. that's really good to know. i should clean this up. i'll get the dustpan. behind the golf clubs. get to know geico. and see how easy homeowners and renters insurance can be. somehow we always leave packing to the last minu

just ask mark billingham, who yeent almost 20 years with british special forces. >> for the securityces it really is a massive headache and a lot of planning and a lot of time, effort, and cost to prepare for this. thank god i'm not on duty. >> reporter: unlike london, where william and kate made their journey to buckingham palace, windsor is a medieval town, a warren of confined streets and tightly-packed buildings, with rooftops and balconies overlooking the procession. >> this is a hell of a job to secure. >> reporter: dai davies is the former head of royal protection. >> it has narrow streets cobbled in parts. how do you secure several miles an very small township and parts which are open and green? >> reporter: roadblocks and barriers like these will stop vehicles from getting anywhere 10ar the crowds. and even with more than 100,000 people expected, the police commander of this wedding assured us today each person will be screened. >> the technology is very different now than it was in en11. and everybody that's coming into eve processional route will go through airport staff s