Gettin' married in the morning

>>> there's the abbey where it takes place tomorrow. in london , it's finally and officially the eve of the royal wedding . it's a cold night there, and already the streets are filling up with people. remember, upwards of a million people are expected to jam into london , see what they can see, hear what they can hear. nbc's kate snow , who will have a better than average vantage point on this with us from westminster abbey tonight. kate , good evening.

>> reporter: we have a better than average vantage point now and the tents are packed four and five deep on the streets around the abbey. there is the possibility of rain in the forecast tomorrow, but no one is letting that put a damper on the big day . late today, a surprise appearance by the groom greeting well wishers on the eve of his wedding. earlier today, kate arrived at the goring hotel, where she'll stay tonight. when she leaves tomorrow morning , her fans may not have as good a view. a white canopy was put up to make sure her wedding dress remains a secret.

>> off the rope, please! rrtd this morning, kate was spotted with prince harry at westminster abbey , one final run through with the bridesmaids and page pois. even camilla came out to say hel hello. among those invited to the wedding, london 's entire diplomating core. in light of attacks by civilians against government forces, the presence of the serious ambassador would be unacceptable and he should not attend. otherwise, the wedding plan s seem to be going without a hitch. all along the procession route today from westminster abbey to bi buckingham palace , people made themselves at home. andrew roberts said some of the traditions we'll see tomorrow go back 1,000 years. how meticulous is the planning for the procession that happens?

>> absolutely split-second. everything has to be absolutely perfect. if you have one or two people out of step, the entire of the rest of the procession gets out of step as well.

>> reporter: the official program for the wedding is online now with a thank you from the bride and groom. they write, we are both so delighted that you were audible to join us in celebrating what we hope will be one of the happiest days of our lives . the wedding hasn't even happened yet, but part of the service tomorrow looks ahead to the future already. it's a prayer that god grant the couple the gift of children, brian.

>> so kate , with a million people expect said, 2.4 billion watching around the world, give or take, is security stifling yet, and if not, is for a moment where it's going to clamp down around you?

>> not stifling yet, although very tight. there are a lot of police out on the streets. roads are closed already this evening. they have already made several arrests of protesters who got out of hand. this procession route is well traveled. it's government buildings , a lot of close caption tv cameras hanging on this route, so it should be fairly well protected, brian.

>> kate snow , part of the team in london for the story all day tomorrow, and you'll be able to see it all on the.

>> announcer: station starting tomorrow morning , 4:00 a.m . eastern, 3:00 a.m . central, 1:00 a.m . pacific with matt and meredith leading the way.