In a 10-part series, BBC broadcaster Barry Davies recalls the most memorable Olympic moments of his 44 years on air from the Games.
I'm sorry this has to be here, but it has had an effect on the Olympics ever since and on life ever since.
At the Munich 1972 Olympics, Palestinian terrorists calling themselves Black September attacked members of the Israeli Olympic team in their quarters at Block G, 31 Connollystrasse, in the Olympic Village.
I can remember waking up on the day in question, turning on German television and seeing pictures of the building. I thought: "What's going on? Why aren't we at the Olympic Games?" It soon became clear.
Members of the gang had killed two members of the Israeli Olympic team immediately and, in a tragedy which went on from 5am one morning until 4am the next, eventually 11 athletes and coaches and one German policeman were killed.
It was the most extraordinary day and, of course, a disastrous day.
A Munich survivor remembers
Israeli swimmer Avraham Melamed survived the attack in a neighbouring apartment, spared by the terrorists (one of whom is pictured above). Now 67, he told his story to USA Today earlier this year.
"I feel a little strange about sort of deriving notoriety from this incident. I feel a little bit guilty. My friends died. I'm not a victim. I'm a survivor.
"They say there was no security. The truth is that the people there did not have guns but it was much better protected than Tokyo 1964, where you could get everywhere, and in Mexico City 1968, where you just had to pay a couple of pesos.
"[After the failed rescue operation] they let us visit the room where they kept our friends. All of their belongings were strewn and there was a huge pool of blood. It was like a dream that you observe from the outside. You want to feel something but all you feel is anger.
"Rationally, we knew that the Germans had zero interest in supporting anything like this. But the whole association of Jews getting killed again on German soil, there was a lot of anger.
"The Olympics were a virgin phenomenon. It's not a virgin any more. Now you have to think about security. Now you have to think about terrorism. Now you have to plan for it. It comes at an enormous price."
The holding of the Games in Munich was supposed to be a chance for West Germany to present itself to the world in a different guise. It wasn't that long after World War II and this was their first real opportunity to do that.
I have heard it said since that German security around the village was lax, but I don't know that I entirely agree with that. It clearly was in allowing the terrorists to get into the village, but it appeared they were helped by genuine athletes who assumed that, because the gang were in tracksuits, they were other athletes who had gone out for the night. They innocently helped the gang get in - which was really sad.
I do remember one journalist, unhappy that he could not get into the village to do an interview, asking at the media conference - with a turn of phrase rather lacking in taste: "How is it I can more easily get into Dachau than the Olympic Village?"
Dachau, the former Nazi concentration camp, was only just down the road. While I don't much care for the comparison, that question never did suggest to me that the security was entirely lax. The problem was more that, at the time, nobody would have conceived of these events happening.
The whole day I remember there being a concentration on one, plain building. It was an unmoving picture, yet so moving at the same time. The horror was in the mind about what had happened, and what might still happen. For British television it was handled quite superbly by David Coleman, who had just the right balance of authority and sensitivity.
The terrorists had asked for the release of 234 people from jails in Israel, but Israel would not negotiate. Eventually, there was supposedly an agreement that the group would be flown out of the country and helicopters were brought in. In reality, the Germans' plan was to ambush the kidnappers.
However, they made a big mistake. They thought there were only five terrorists - but there were eight.
Initially, the message came back from the airport in the early hours of the next morning that the operation had been successful and the hostages had been rescued. Later on, the truth came out. They didn't have enough snipers to take out all the terrorists. The hostages were dead.
The debate then was: what do the Olympics do? How can you go on having sporting events when people are being killed? I'm sure it was hotly debated among every team, every journalist and throughout the world.
I think the right decision was made. I thought then, and I still think, the Games had to go on. Otherwise it would have been "open sesame" for things like this to happen in the future.
Sadly, the aftermath was handled poorly by the International Olympic Committee (IOC).
What happened next
Memorials to the victims now stand outside both Munich's Olympic Stadium and the apartment building itself, though calls for a tribute in their name at London 2012 have been rejected by organisers.
Counter-terrorism efforts worldwide increased markedly - and in some cases were brought into being - as a result of the tragedy in Munich.
In the aftermath of the attack, Israel's intelligence agency, the Mossad, began a campaign to trace and kill the surviving Palestinian terrorists.
At a service of remembrance where empty chairs had been left for the 11 athletes who died, there was not one representative of any Arab nation.
In his speech, the then-IOC president Avery Brundage contrived to draw together the killings and a separate problem that had occurred before the Games - involving
Rhodesia's inclusion in the Games.
He somehow connected the IOC being 'blackmailed' in the latter case with the deaths of Israeli athletes who had been gunned down. It made for a very, very uncomfortable listen. To link the two was bizarre.
After the memorial service, there was a fairly brief allowance of time before we were dispatched again to where we had to be. I frankly have no idea where that was and I suspect a lot of people went off having no idea what they were supposed to be doing.
But if you're an athlete competing for a gold medal and a decision is made for the Games to go on, then you must also go on and that effort to win a gold goes on - as does the effort to write the story and commentate on the sport.
A final note. David Miller, in his official history of the Olympics, records that as people filed in for the memorial service, Greece's King Constantine - a member of the IOC - was accosted by a man. That man was Jesse Owens, famed for his four gold medals at the last German Olympics, in Berlin 36 years earlier.
Owens simply said: "The Games must go on."