Footage of the first explosion at the Boston Marathon, recorded by a reporter doing a piece at the finish line, evokes the same sense of shock and rushing realisation as similar recordings made when the bomb went off at the 1996 Atlanta Olympics.

The waves of this horror flow out. They reach us, distant observers. They reach other imminent sporting gatherings, such as Sunday's Virgin London Marathon.

Today, in the wake of the attack in Boylston Street which cynically disfigured an event composed of some of the purest and best of human motivations, organisers of the London race reiterated their determination that their show would go on as planned.

"We have reviewed and will continue to review our security arrangements with the Metropolitan Police and other authorities," said an official statement.

Nick Bitel, the London Marathon chief executive, added: "We want to reassure our runners, spectators, volunteers and everyone connected with the event that we are doing everything to ensure their safety and that the Virgin London Marathon 2013 will be an outstanding success."

As the reporter at the finish line, who had run the Boston Marathon three times himself, commented, the usual feeling to be had there for competitors was one of having completed a home run at Fenway Park, home of the Boston Red Sox.

The tide of pictures and footage on social media and news outlets now testifies to the different emotions which predominated in the minutes after those wickedly timed explosions.

Of course, there are wickedly timed explosions going on all around the world. Pain is pain, grief is grief. But there is something very awful about the sudden juxtaposition of something so evil with something so good.

A female runner reacts with bewilderment in the aftermath of the Boston Marathon bombing

As the International Association of Athletics Federation (IAAF) President Lamine Diack pointed out, "what makes this incident so vile and its planning so incomprehensible is that marathons the world over are about selfless acts of human generosity. Millions of dollars are raised for charity every year by participants in road races. The events themselves are administered by thousands of volunteers."

A statement issued by Nova International, organisers of the Bupa Great Run Series, put it like this:

"Mass participation running events are celebrations of community spirit and endeavour and for this horrific, unprecedented incident to occur is a tragedy."

The scene at the finish of the Boston Marathon after the double bomb blast

The outrage is clearly expressed - but, sadly, this was not an unprecedented incident.

On April 6, 2008, a suicide bomber detonated a device at the start of a Sri Lankan marathon in Waliweriaya, killing at least 15 people, including the Highway Minister Jeyaraj Fernandopulle. The attack, which was blamed on the rebel group the Tamil Tigers group, also injured almost 100 people.

On May 1, 2002 a car bomb exploded near the Real Madrid stadium hours before the home side were due to play Barcelona in the European Champions Leagues semi-final. A second car bomb exploded a half hour later about a mile away. The Basque separatist group ETA took responsibility for the attack, which injured 17 people.

In 2010, football followers in Kampala, Uganda were the target of bomb  blasts while they watched TV screenings of the World Cup final between Spain and the Netherlands. At least three bombs exploded on two sites - a large sports field, and a restaurant - and more than 50 people were reported killed.

The Washington Post reported that militant Somali group al-Shabab, linked to al-Qaeda, claimed responsibility for the attacks.

The Atlanta Olympic bomb went off at 1:20am on July 27, 1996 in Centennial Olympic Park, killing two people and injuring more than a 100 others.

Eric Rudolph, a former explosives expert for the United States Army, confessed to placing the bomb in front of a video screen in the park. He called in to 911 twice before the bomb was scheduled to go off to warn officials about the bomb, according to an interview in Sports Illustrated.

The best known footage of this incident featured an interview by ARD TV Germany taking place with US swimmer Janet Evans, whose long Olympic career was being celebrated at the Swatch Pavilion within the Park.

The sound of the explosion, a breaking glass, breaks in upon the conversation, and the swimmer breaks away towards the camera with a look of distress on her face as others peer out of the window to see what has happened.

A memorial gathering at the site where spectator Alice Hawthorne was killed by the bomb which went off in Centennial Park at the 1996 Atlanta Olympics