As an athlete who hopes to figure strongly in those London Games, and as someone who lives just round the corner from King's Cross station, where much of the post-bombing mayhem took place, Williamson has felt those emotions particularly keenly.
The 19-year-old sprinter had just left home en route for a training session at Crystal Palace on Thursday when he became caught up in the events which, like so many others, he found initially hard to comprehend.
"I was walking to King's Cross station as usual when I started seeing all these people with black stuff on their faces," he said. "They were all dressed up in suits. I didn't know what to make of it. When I got to the station there were police there, and ambulances, and fire engines, and they were cordoning it all off. We all had to move back and stand across the road from the main entrance.
"A policeman told me there had been some kind of an explosion in the Underground, so I started looking for a bus, but then I was told the buses weren't running, so I went back home. I still didn't know there had been a bomb. But when I phoned up my coach, Lloyd Cowan, to tell him I couldn't make it, he said: 'Yeah. I know. Have you seen the television?'"
Williamson, a regular churchgoer, has felt the impact of Thursday's attacks keenly. This weekend, however, he will be able to think about other things as he takes part in his first senior AAA Championships, which double as the Norwich Union trials for next month's World Championships and the Commonwealth Games next May.
As Britain's first major Olympic sport event since the Games were awarded to London the trials should have a "value added" feeling. For younger athletes, the competition that gets under way this afternoon leads not just to Helsinki, or even to the Beijing Olympics three years hence, but to what is now a large patch of scrubland in the middle of Stratford and will be, in seven years' time, the epicentre of Britain's Olympic offering.
Within seconds of the International Olympic Committee awarding the Games to London, Cowan's phone became jammed up with calls from his group of predominantly young competitors. "My phone was being flooded with text messages," Cowan said. "Most of our youngsters were buzzing. To think of the Olympics being held on British soil was amazing. They were all saying 'We've got the Games! Wow!'
"I said to them, when those Games come around, you will all be in your mid-20s. Now you've got something to really look forward to and work towards. Having the Games on our home turf - that's 10 per cent extra in competition. Our athletes will want to do themselves and the nation proud. I've told my group it's an experience they will have only once in their life, and it's going to be fantastic. If they don't make it there as athletes, they have to be volunteers..."
Williamson, however, has no plans to enter the voluntary sector. He aims to be there by right at the age of 27, and he would like to start his Olympic experience in Beijing three years from now, either with an individual 100 metres place or a spot in the relay.
Given the fact that the men's sprints are currently one of the hottest growth areas in British athletics, that will be no easy task. But Williamson is going for it, just as he went for the AAA Under-20 title last weekend and came out not just with a winner's medal, but a hugely promising personal best of 10.24sec.
That achievement is all the more remarkable for the fact that he has only been training in earnest under Cowan's direction for the last year. "He's a raw young talent," Cowan said. "He's only started doing work in the gym in the last few months. But he's got this natural ability to win. It's a special gift, and I never want him to lose it."
One thing the young sprinter has had to lose, however, is his aspiration to pursue a footballing career. As an extremely swift winger, Williamson had dreamt of playing for his favourite team, Arsenal. But he was forbidden by his mother, Beverley, from playing for one of the many Sunday teams clamouring for his services, because it would have prevented him attending regularly at the family's place of worship, the Kensington Temple in Notting Hill Gate, west London.
But he has not, according to Cowan, lost his habit of being late. Williamson chuckled in acknowledgement. "That's just me," he said. "I hate waiting about." There has certainly been no hanging around for him this season. After making his mark at the AAA senior indoor championships, where he reached the 60m final, he won the AAA Under-20 60m title with a personal best of 6.73sec.
That potential was underlined in Bedford last Saturday as he defeated Craig Pickering, the 18-year-old whose run of 10.22sec earlier this season has established him at the top of this year's European junior rankings.
Williamson, Pickering and Alex Nelson - the first three home in the AAA Under-20 event - will travel to Kaunas, Lithuania, as the three leading-ranked runners in the European Junior Championships which take place there on 21 to 24 July. Seven years on, it is tempting to picture them in an Olympic setting.
For now, however, Williamson is looking forward to running against the likes of the Olympic sprint relay gold medallists Mark Lewis-Francis, Darren Campbell and Jason Gardener for the first time. His ambitions are hardly conservative. "I want a personal best, and a medal," he said. That's the spirit.