TINY margins are what the Olympics and Paralympics are all about.
A millimetre here, a split-second there ? these are the differences between medal winner and also-ran.
But any British athlete who experiences success this summer will owe a great deal to a dedicated team of unsung heroes pushing them on to achieve these tiny margins.
For GB wheelchair basketball star Simon Munn, 43, this means the coaches, physios, mechanics and nutritionists.
But he is also indebted to a woman who helped him bridge the gap between life and death in 1990.
Simon was walking home after a night out when disaster struck.
Simon said: "I took a short cut across the railway track. I got my foot trapped in the last set of tracks... and waited for a train to take it off.
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"I only had to wait a few minutes ? probably about five ? to watch the train take my foot off.
"It took all my strength to crawl the long way to get to the side of the road and try to flag down a car.
"Finally a pizza delivery driver pulled over and he waved down a lady motorist. She used a golf club she had and the pizza guy's belt to make a tourniquet to stem the blood flow. She probably saved my life."
Simon later learned that by the time the ambulance arrived he had less than two pints of blood left in his body. The norm is eight.
A few years later, by which time Simon had played for GB in his first Paralympics, he found the bar where the woman was working.
He said: "I didn't recognise her when I walked in, but she knew it was me straight away and came over. It was just something I wanted to do. I wanted to say thank you."
Simon has gone on to play for wheelchair basketball teams throughout the UK and in Italy. London will be his SIXTH Paralympics, with one silver and two bronze medals already to his name.
Simon, a full-time player, said: "It would be interesting to know what the lady thinks about my Olympic career. Hopefully she'd feel she'd had an important part to play in it."
Injured Simon, who played football before his accident, was badgered to watch wheelchair basketball by his hospital physio, who was married to a former GB player.
He said: "I didn't class myself as disabled. I wasn't interested in some game for disabled people.
"But I saw guys knocked out of their wheelchairs as they fought for the ball. Halfway through I had stopped seeing the wheelchairs.
"I just saw the sport and knew it was for me. I fell in love with it."
Simon now lives in Brighton with girlfriend Michelle Hooker, daughter Terri, 17, and two-year-old son Henri. He plays for the Capital team in London and spends three weeks out of every four involved in tournaments in the UK and abroad.
The training is gruelling. One endurance session involves him and his team-mates repeatedly dragging weight-laden sledges behind their wheelchairs on a race track.
Simon said: "Training can be more intense than for able-bodied athletes. They can do one day working on their top half, then the next work on their bottom half.
"With wheelchair athletes it's all upper body, so any rest is crucial."
Taking gold at his home Paralympics would be the pinnacle of Simon's career. If the team do win a medal, there sadly won't be room on the podium for all the people who have helped get them there.
It will be down to the likes of Murray Treseder, head coach for the GB wheelchair basketball team, to the experts at RGK, led by boss Russel Simms, who provide Simon with his ?4,000-plus Interceptor Extreme titanium-frame wheelchair.
And to the anonymous lady in Milton Keynes who made the greatest difference of all.