The allocation of Olympic tickets in the first round ballot left Mel Lintott with something of a problem.
Yes, she had managed to get her hands on two highly covetable tickets for one of the biggest nights of the athletics competition, a session that would see Jessica Ennis and Mo Farah's bid for gold, the men's long jump and the women's 100m finals. But she only had one spare ticket, and didn't know which of her three brothers to offer it to.
She thought about giving it to the highest bidder but that seemed a little unjust. Then a friend had an idea. "[He said]: 'Tell them to do a 100m running race. It's only fair and apt that that should be the measure of their success.' So it was decided upon. And here we are. Today's defining moment."
On a hot early evening in an east London park, Mark, 32, and Max, 25, limbered up, threw affectionate insults at each other while pretending they weren't taking it too seriously. The withdrawal of their other brother Rory – "he wasn't up for the competition" – made it a straight head-to-head fight, youth versus experience.
Had neither considered backing off? Mark, a teacher from south London, snorted.
Max said: "Definitely not … When this came up I don't think any of us were going to say no. The thing is, it's fine now and this is all very relaxed, but there are plenty of weddings and birthdays to come when this really may come up again."
"If you lose," interrupted Mark, before correcting himself, "when you lose … I'm never going to let you forget it."
"We're rather a competitive family," said Max, apologetically.
Both, it turns out, have reason to fancy their chances. What was Mark's sporting history? "Just a bit of cricket, rugby, hockey, tennis" at school and university, more recently a couple of triathlons and last year's London marathon.
Max, meanwhile, reminds his brother that he had competed in national athletics championships as a child. Now he does "tennis only. And running. Well, a lot of running."
How would their sister feel for the loser, knowing she had been the cause of their humiliation? "I'll probably just wind them up about it," she said.
To the main event. A couple of friends turned up to act as race marshals. One downloaded a GPS-based app for his phone and measured out an approximate 100m, dropping a boat shoe to mark the start. Mel and a tree held the finishing tape. There is a tense crouch, a "Set!" and the sharp burst of a whistle.
Very soon it was all over, if not quite so soon as it would be for Yohan Blake. Max, taller and rangier, got the better start and adopted what might be called an Eric Liddell technique – head back, eyeballs out, attention firmly focussed on the finishing tape – in this case a stretch of blue ribbon Mel acquired at work.
His older brother, more compact, gets a start worthy of Usain Bolt - not quite textbook, in other words. He can't recover the ground, and hit the tape several metres behind his younger brother.
Their sister presented the ticket. "It's not for you," she says to Mark, who declared himself "genuinely really gutted".
He adds: "I had a feeling that I might have got quicker as I have got older but I definitely haven't."
Wasn't there a chance this would put a strain on their relationship in future? "Definitely!" said the delighted victor. "This is coming up every family meal for the rest of our lives."
