Watching Usain Bolt go into the record books with his win in the 200m final, what was so striking was not just his incredible talent and the character he has shown in getting himself back from a place where he was struggling a month ago. It was also his mastery of knowing how to get himself in the right state to perform at the best of his ability.
That, in his case, is to relax, to laugh, to joke, to talk to the bag carrier, to smile, and all that sort of stuff. But if you watch his face, with just 30 seconds or a minute to go before that final, he is completely focused. He is completely in the zone.
This ability to switch it on and off so quickly is extraordinary. I haven't seen anyone with the ability to do that.
People mustn't think that he's laughing and joking and turns up and runs. For that split second –where you have to get into the zone, to stand behind the line, to deliver your performance – he is as focused as everybody else in that race.
He is able to do that because he can switch it on and off in a heartbeat. He is a master of it. He is a master of putting himself in the right state to perform.
Quite clearly, we are seeing the greatest sprinter of all time. But there's an argument now that we're witnessing the greatest athlete of all time.
We've had this discussion at this Olympic Games about who is the greatest Olympian of all time and I don't think we should judge that just on how many medals you have won. I think to be the greatest Olympian of all time you need to have won an Olympic title and to have successfully defended, which Usain has now done twice over, with the 100m and the 200m.
But you also need to have done something special. You have to be more than the sport, to be a global superstar – to be somebody who changes history. And Usain Bolt, I believe, is the first track and field athlete who has truly ticked those boxes.
We are so privileged to watch this man. It's very hard to find superlatives for him.
It's slightly crass to say thing like "amazing, fantastic, incredible". We need to find a new word for him. It's not just what he does. It's the way in which he does it.
He admitted he is not 100 per cent, so what he had to do in London is dig deep. And he's proven that he is the complete package.
He's shown in London that as well as having a phenomenal talent, he also has this incredible resilience and ability to turn things round.
He has done that in the last four weeks and proven what a supreme competitor he is.
Although he made it look easy, there was no doubt he was not 100 per cent here, especially in the 200m. He wasn't laughing and smiling and dropping his arms with 15m to go. He knew he had to race. In both races here, he knew he had to run to beat his training partner. And he didn't just beat Yohan Blake; there was daylight between them.
We must be careful not to take Usain Bolt for granted. He was struggling four weeks ago and proved to the world that he is more than just a talented athlete. He is truly the complete package.
Home crowd can lift Farah to be best British performer of Games
I don't think the 5,000 metres is going to be a walk in the park for Mo Farah tonight. Just because he won the 10,000m so magnificently last Saturday, we mustn't necessarily assume that he can just turn up and win another gold medal.
I think if he does win another gold, then he will be the British performer of these Olympics. There would be no doubt about it.
If Mo does the 5,000m-10,000m double, he surpasses any performance by any other British athlete at these Games, in my opinion. It would be better than what Jess Ennis did in the heptathlon because it would be a double.
It's a subjective discussion as to who is the greatest Olympian and also the greatest performance. But I think to be crowned the greatest performance of the Games you need to have done something extraordinary, like Usain Bolt has done in the 100m and 200m, and like David Rudisha has done with his world-record run in the 800m.
From a British perspective, that would have to be Mo Farah if he won two Olympic gold medals. I know Chris Hoy has won two golds at London 2012, but one of those was with other people. So just on that fact alone, you would have to put Mo on top of the pile.
It's a tough ask in any situation for an athlete to come back from the 10,000m and go and win the 5,000m. But it's an even tougher task for an athlete to do that in a home Games – because of the expenditure of energy, the attention, the magnitude and emotion of what he did last Saturday. It was just a magnificent performance.
I think we saw in the heats of the 5,000m that Mo looked tired. And of course he should be tired. So I don't know how he's going to do in the final of the 5,000m.
If I'm honest, I don't know enough about what's it's like to run a 10,000m and then a 5,000m. What I do know is that he is a man who has the ability to run fast at 5,000m – he's the world champion at the distance – but also he has the ability to be inspired by the crowd and the occasion.
We've seen throughout the Games what the home crowd can do. I think if Mo Farah were to win the 5,000m, he would certainly credit having a home crowd to get him through it.
Roger Black is an ambassador for Scottish Widows, the official pensions and investments provider for the London 2012 Olympics.