More than 80 years ago, in 1924, there was a young man in Edinburgh called Eric Liddell who ran so fast that people called him 'The Flying Scotsman'.
Eric practised hard, running every day and timing himself with a stopwatch to see if he could go even faster and beat his own record.
In those days there were no such things as trainers with comfortable bouncy soles and Eric wore only canvas shoes - but he ran like the wind.
He looked quite peculiar when he was running because he was concentrating so hard: his head went back and his mouth fell open and his arms flailed about.
When people saw Eric's head begin to fall back they knew he was thinking of nothing but how to get to the winning post.
He was best at short, fast races and the race he liked running the most was the 100 metres. And Eric wasn't only a runner. He also played rugby for Scotland and was an excellent cricket player.
In fact, Eric was brilliant at every sport he tried. But in 1924 the big event that was on everyone's minds was the Olympic Games.
That year they were to be held in Paris - the capital city of France - and in Scotland they all knew that the star of the running races would be Eric, who was in the British Olympic team. Could Eric be the first Scotsman to win an Olympic gold medal?
Eric practised harder than he had ever done in his life. When he wasn't studying science at the university, he spent all his time on the athletics tracks, running.
People watching him marvelled at how fast he could run but they were often surprised that he was never vain or boastful. In fact, he seemed always to be happy when someone else was good at something and would smile and clap when they did well.
Then, just a few weeks before the Olympic Games, the letter came.
It was the timetable of all the races. Eric opened it at breakfast and looked down to see when his race, the 100 metres, would be run.
And his heart sank - because the race was scheduled for a Sunday!
Eric knew that he would never, ever run on a Sunday. He was a Christian and Sunday was the Christian day of rest, the Sabbath, when people take time to think of other things than working or winning races and getting medals.
He wondered if they would perhaps change the time of the race to another day.
But it was impossible: there were hundreds of countries taking part in the games and the organisers of the Olympics couldn't change the timetable just for one person.
There was one that wasn't being run on a Sunday. So he signed up for the 400 metres race. But he had never tried it before and he only had a short time to practise running over longer distances.
His family were worried - 400 metres was a long stretch for someone who was used to running very fast over a short distance. But Eric went on practising - he knew he could only do his best.
When the teams arrived in Paris for the Olympics, the crowds came out to greet them. They hung flags from the houses and cheered loudly as the athletes' buses drove through the city.
Eric felt overjoyed to be there and he knew he was part of a brilliant team of runners who all hoped to come home with lots of medals - silver and bronze would be good but best of all would be gold.
His friends on the team couldn't help being a little worried about Eric.
After all, the 100 metres was his best race and he wasn't running in it. Could he possibly win a longer race? A lot of people thought it was impossible.
The day of the 400 metres race arrived and Eric went down to the starting blocks.
He felt quite relaxed but he didn't really think he could win the race. He thought maybe he could come third and get a bronze medal to take home.
As he crouched down to put his feet in the blocks he was concentrating hard. Just then, an American man rushed out of the crowd of spectators and slipped a piece of paper into Eric's hand.
Eric just had time to read what was written on it. It was a line from the Bible which read: 'Those who honour me, I will honour' - meaning that God will look after those who put him first in their lives.
Eric felt himself grow bold and confident as he read it and when the starting pistol sounded he gripped the piece of paper in his hand tightly. Then he ran.
His family and friends held their breath as they saw his head fall back and his arms begin to swing wildly: this meant that Eric was running as fast as he was able. He was a blur of feet and arms as he ran on and on, flying past the other runners. Two of them actually stumbled and fell over in their effort to keep up with him.
He hit the finishing post to the loud cheers of the crowd - he had won!
As Eric Liddell, the gold medalist, stood on the podium, he still clutched his piece of paper. He remembered how he had kept true to his resolution never to run on a Sunday and he thanked God for looking after him and for the surprise of his life - an Olympic gold medal for a race that everyone thought he couldn't win.