They roared him on just as loudly as they did Hannah Cockroft, who won gold in theT34 100m in a Paralympic record of 18.06sec, and Sophia Warner, who came fourth in the T35 200m in a personal best time, and 18-year-old Rhys Jones, eighth in the T37 200m.
Derenalagi did not even make the final of his event, the F57/58 discus. The crowd did not discriminate. His best effort was 39.37m, which is almost four metres down on his personal best. Only the top eight throwers got to take their final three throws and Derenalagi came 11th. Disappointed as he was, he will cope.
Curious as it may seem, there are rules about how to report on these Games. Paralympics GB advises journalists that competitors should be "portrayed as elite athletes first and foremost, rather than people who have overcome great adversity". The understandable worry is that it would be patronising to focus on an athlete's back story. It is better, surely, to treat each as an individual. All of them have their own goals. For Cockroft nothing less than gold would do. As she said herself: "I knew deep down that I could beat all the girls." She was almost a second and a half ahead of the silver medallist, Amy Siemons from the Netherlands.
What Derenalagi has done to get here is so remarkable it deserves to be celebrated, not tiptoed around. He has said himself that his main ambition is to "inspire others", that he believes doing that would mean more than winning a gold medal. "I want to put a smile on someone's face, especially someone who has lost a limb, who thinks they can't do anything. To inspire someone like that would be more rewarding to me than anything."
Derenalagi, 32, lost his legs – they were amputated below the knee – while he was serving with the army in Afghanistan. His Land Rover was hit by an improvised explosive device. The medical staff had given up on him and were about to put him into a body bag when one of them detected a weak pulse. He spent eight days in a coma, three weeks in hospital. Now, with the help of the army's Battle Back rehabilitation program, he is a proud Paralympian.
That is a common sentiment among the British track and field squad. The 21-year-old Aled Davies, who won the team's first athletics medal when he took bronze in the men's F42/44 shot put, said something similar. Eight years ago he had been watching the 2004 Athens Paralympics on TV, when he turned to his family and told them: "One day I want to be on that podium."
"I didn't really recognise myself as disabled but I thought: 'That guy is the same as me. he has got what I got.' I remember telling everyone: 'I'll be on the podium one day … one day.'" That day was Friday.
Davies was born with hemimelia of the right leg, which means he has "no ligaments, no tibia and no foot". It is, he said, "all held together with metal". Like Derenalagi, Davies hopes he has inspired one or two people in similar situations. There may be other kids watching him on TV, dreaming of glory, just like he once did. "It is all about inspiring a generation at the end of the day. I hope we can get a lot more people in the sport and make Paralympic sport a big thing in Britain. All these people here just gives a little taste of how many people are going to know about it."
The atmosphere inside the stadium was, the Paralympians all agreed, unlike anything else. Shelly Woods, who finished third in her heat of the T54 5,000m, was the first Briton out into the stadium in the morning session. "I've never experienced anything like it, it was immense." David Weir, going in the men's version of the same event, coasted through his own heat with insouciant ease, taking a tip from Usain Bolt's book and striking a pose as he crossed the line. The roar that accompanied his last lap was the loudest of the day.
"It was just incredible. As soon as I came out of that tunnel the whole stadium erupted," Davies said. "They didn't know who I was. But I was competing for Great Britain and they just started screaming. And I thought then: 'Wow, it's here, let's go out and do it.'" He reckoned that he had to slow down his technique and "go at 75% of my effort because the crowd was carrying me so much, when I was going at 100% of my effort I couldn't control it. In that atmosphere and with that adrenaline my heart was going through the roof."
Davies had been a swimmer, following his elder brother's lead, and had been on course to compete in Rio 2016. But he decided he wanted to compete at his home Games and went along to a talent identification day in 2005. "Somehow I had a talent for throwing things about." He has deferred his third year of study at university to train full time for these Games, a decision that looks as if it will pay off. His main event is the discus, which takes place on Sunday
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image: © Fighting Irish 1977