Alex Witt | April 20, 2013
>>> over to london now on the eve of the world's largest marathon. that's right. the world's largest marathon. 36,000 runners will compete tomorrow. officials are significantly boosting security measures fogle this week's attack in boston . nbc is joining me from london . what can you tell us about all these extra security plans considering everything that's happened this week?
>> hey, alex, good afternoon. london 's police said they increased the number of officers out on the route by 40%. that also would be more sniffer dogs out. remember, they have a 26 mile course through london that they need to protect. that's wide open , attracting hundreds of thousands of spectators, and everyone is thinking about what happened in boston . not just in terms of security arrangements, but also the competitors who have been telling me tomorrow they'll be racing for boston 's victims.
>> reporter: the london marathon winds around some of the city's greatest landmarks, buckingham palace , big ben , and tower bridge . 36,000 people will take part and despite the boston attacks, they're more determined than ever.
>> i think it inspires you more. you're just not going to let people put fear into you. bostonians are pretty resilient and, you know, we're going to move on. become stronger.
>> reporter: tens of thousands of people are expected to line the course cheering on the runners. security preparations have been under way all week, but since boston the number of officers have been increased by 40% and london 's police have been in close contact with the fbi.
>> the most important thing that there is no link between the boston marathon and the london marathon . however, people need to feel reassured on sunday when they come out to see their friends, family, and beloved, and that's very important to us. they can see a high visibility of police on the streets.
>> reporter: not just on the streets. london is one of the most watched over cities in the world with hundreds of thousands of cameras recording every move. but organizers are determined to keep the marathon fun like last year prince harry will hand out medals to the winners. tatiana mcfadden could be amok them. she won the boston women's wheelchair race and she's competed in london as well saying the city will be in her heart.
>> running for london i'm going to be dedicating the race to the people in boston and it's about trying to show that, you know, we're not going to let this event win.
>> before the start of tomorrow's race there will be a 30-second silence and organizers promising every competitor who make it is over the finish line , they will donate $3 to the boston victims fund because this has really dominated the news over here all week. just look at some of the today's headlines. you can see this one here, the hunt with some of those dramatic images from yesterday's siege. and on the front of "the guardian" dead and alive with the two suspects taking center page. there really has been an outpouring of support for the people of boston and a lot of relief that it is finally over. alex?
>> the indomitable human spirit , pretty darn inspiring. thank you very