There aren't many rules to Olympic speed-skating.
Get around the rink as quickly as possible. That's the gist.
The fastest man or woman wins.
But there's one rule you have to remember -
there are only two lanes on the speed-skating track
and you have to skate one lap in one lane
and then the next lap in the other.
It's simple, really. Alternate.
This lane, then that lane, then this lane, then that lane.
Lap after lap.
The whole sport is about rhythm.
Dutchman Sven Kramer didn't need telling the rules or rhythms
of speed skating.
By the time of the 10,000m race in Vancouver in 2010,
Kramer hadn't lost in four years.
Sven Kramer!
He'd won 18 consecutive 10,000m races and had a gold medal
already from the 5,000m, won the previous week.
But on a fateful February day in Canada,
Kramer forgot his rhythm.
JUDGE: Ready.
Kramer was an overwhelming favourite in Vancouver.
He was last on the track, from eight pairs of racers.
Kramer was expected to destroy his Russian partner Ivan Skobrev
and to drift comfortably inside the time of Korea's Lee Seung-hoon,
as well.
For 16 laps everything was perfect.
Skobrev was a dot in the mirrors. Kramer was keeping bang on track.
His rhythm was metronomic and his style exquisite.
Counting down the laps, he had everything right.
This lane, then that lane.
Then 16 laps to go, then 15.
14, 13, 12, 11, 10, 9, 8.
Whoa! What's happened here, Sven?!
Rewind.
Speed skaters have a close relationship with their coaches.
The men and women in the tracksuits stand by the side of the ice,
to offer encouragement and direction.
They also tell the skaters if they should be in this lane or that.
Kramer's coach Gerard Kemkers had done all of the above for 16 laps.
But then, he had a moment of madness.
As Kramer approached the changeover, after 6,600m of plain sailing,
Kemkers shouted at Kramer to go to the inside lane.
But Sven was sure he should be heading out.
The 23-year-old Kramer yielded
to his older and more experienced coach.
But crucially, his own instincts had been right
and his coach's were wrong.
Clean-living Sven Kramer was now on the wrong side of the tracks.
Kemkers knew it almost instantly,
but was powerless to go back in time.
The South Koreans knew it, too.
Watching from the middle of the track, they knew Kramer
was going to be disqualified.
The only man who didn't know it was the man in the polished
black and orange skating suit, who thought he was heading
for a gold medal.
He flew over the line, smashing the Olympic record,
but now Kemkers had to come clean.
Kramer learnt that he had lost the Olympic gold from the man
who had caused the calamity.
And he was not happy.
Not happy at all.
You'd think a calamity on this scale would mean the end of the road
for an athlete and their coach.
Kemkers had let Kramer down in the most public way imaginable,
on the biggest possible stage.
But Sven dug deep and forgave his coach.
Despite some obvious tensions, the duo stayed together.
And Sven was rewarded for his patience four years later,
at the Sochi Winter Games, when he won two gold medals
under the guidance of Kemkers.
All's well that ends well?
Hmm, not quite.
Just five weeks after Sochi, Kramer dumped his coach.
As they say, it's easier to forgive than to forget.