According to Amy Lawrence, who had been covering the match for the Observer, the reason everyone knew something was wrong was that Muamba, out of the current run of play, suddenly "fell like a tree trunk. He didn't put his arms out to break his fall, or anything, he just dropped".
It was seconds before other players noticed. Rafael van der Vaart, a Spurs player, was the first to do so, and frantic signalling to the pitchside medical teams brought on the men in green.
Spurs had five fully medically trained assistants pitchside that day, and there was, as ever, aid from the St John Ambulance unit.
Instantly given oxygen and professional CPR, Muamba's chances were already raised.
What was happening to Muamba at this time, according to Professor Sanjay Sharma, a cardiology specialist at St George's University Hospital, London, was "ventricular fibrillation. Rapid chaotic electrical activity within the heart. It means the heart stops its usual pumping function; good oxygenated blood should be pumping from the left ventricle, coming back to the right, but suddenly it's not. Which, after a short while, is not usually compatible with life."
Muamba was lucky. Sitting in the stand that day with his brothers was Spurs fan Dr Andrew Deaner, consultant cardiologist at the London Chest Hospital. "I noticed that Fabrice Muamba had collapsed and I saw people running on and starting CPR. I turned to my brothers and said 'I should help' and they agreed." In another piece of luck, he was allowed on the pitch: stewards can be tough, but Deaner, after arguing briefly with two young men who "didn't want to know", found an older steward whom he knew and persuaded him to give him access. As soon as he arrived on the pitch, Deaner "could see they were doing very good CPR. They had the defib ready."
Muamba was given 15 defibrillation shocks in all: two on the pitch, one in the tunnel, 12 in the ambulance. CPR is fine, apparently, for manually persuading the body to pump oxygen around for a bit, but the heart needs to be jump-started with a 300-joule electric shock. In total, Muamba was to take 4500 joules in those 78 minutes.
18.19-19.01: TUNNEL/AMBULANCE
According to Sharma, this is where something remarkable must have taken place, thanks to the presence of Deaner.
There was a squad of medical experts and friends there already. Spurs' club doctor, Shabaaz Mughal, and paramedics Peter Fischer and Wayne Diesel, who had been so involved in the first six minutes, and Bolton physio Andy Mitchell and club doctor Jonathan Tobin, a personal friend of Muamba.
Sharma said yesterday the decision to take Muamba to the London Chest Hospital in Bethnal Green - almost 12km away - rather than the North Middlesex, much nearer to White Hart Lane, may have helped to save the footballer's life.
"I can only imagine that it was down to Dr Deaner, because he worked there. The amazing thing is that he persuaded the ambulance to change plans: ambulancemen don't normally like to do that. But it was vital, I think. Bethnal Green has equipment which can make a great difference. Ambulances don't have them, and the other hospital wouldn't have."
It was a difficult journey through north London. One of the vehicle's paramedics apparently had to hold the waist of Bolton's doctor, Tobin, while he fought to administer available drugs to available veins, because the pitchside doctor still had on his football boots, and studs slip on metal.
A further 12 defibs were carried out during the journey. "It's a remarkable amount of work to be done on a body in such a time, and a remarkable body to have taken it," Sharma said. "I'm still rather amazed.
"The brain is your hard drive. If it's allowed to conk out, it's the end.
"Had this happened to most chaps, in the average situation, the survival rate would be 11 per cent. If you get specialist help, as he did, it's something like 64 per cent."
Shortly after 7pm local time, the ambulance slewed around the last corner in Bethnal Green.
19.01-19.31: HOSPITAL
The London Chest Hospital has teams of cardiologists, brain specialists and "intensitists". Some had been listening to the match on the radio, wondering whether they might get the call. The journey had been 9.5km longer, on a Saturday teatime, than it might had the ambulance made a routine trip to the North Middlesex, were it not for the intervention of Deaner.
Deaner said: "We went straight into the lab and I put a bigger line into a vein under his shoulder blade and quickly scrubbed up. We got access to arteries and a bigger vein and carried on giving shocks and drugs."
Tobin, Muamba's team physician, was suddenly out of the loop. "Once we got to the hospital I was no longer part of the hands-on crew and it was when I took a step back that everything that just happened hit me." Fabrice Muamba was in the best place possible, perhaps in the whole of Britain, even though he wasn't to know it then.
19.31: HIS HEART STARTS WORKING AGAIN
Against all expectations, Muamba regained consciousness on the Monday after his collapse. He recognised his fiancee, Shauna Magunda, and asked after their son Joshua. Within hours he had talked to a teammate and expressed dismay to his father that his collapse caused the match to be abandoned.
By Tuesday, Muamba was declaring himself "fine" but he remains in intensive care and, according to his family, faces a long road to recovery. Experts say the swift action of medics at the scene undoubtedly helped. Deaner said the London response had been "faultless: one thing after another just went right." He visited Muamba shortly after his awakening and said he'd been moved to tears at the speed and strength of the player's recovery.
"I understand you're a very good footballer," Deaner whispered into Muamba's ear. He was rather taken by the dry response, the first piece of humour from a grim afternoon. Muamba replied: "I try."
- Observer