Alternatively, you could put the question to Keith. How did you end up with two Olympic medallists in the family? And he answers, smiling and bemused: "To be honest, I ask myself that same question all the time too."

Or you could start with Alistair’s first ever race. The first signs of greatness? Hardly, as Keith recalls: ‘When I first took him to a crosscountry running race, it was a schools race, Saturday morning, he was nine years old. There were about 450 kids across all age spectrums; Alistair came about four hundredth. It was a very mediocre but gutsy performance.’ He remembers in particular the sight of his young son, all red-faced, puffing his way up a hill. And also this: ‘In the car on the way back, Alistair said: 'I really enjoyed that. But I think if I am going to get good at it, I need to be not quite as chubby as I am. I am going to start eating potatoes and stop eating chips, and for puddings I am going to eat fruit.' The remarkable thing is that he did."

This was the mark of young Alistair. "An interesting, driven character," is how Keith describes him. For his A-levels, he did maths and the three sciences, but taught himself further maths as a fifth A-level at home. "He had to do everything. He qualified Grade A singing, played the flute. Even as a tiny child, with reading and stories, he wanted more and more. If he fell asleep while you were reading a story, he could tell you exactly where you were in the story the next day. And when he was tiny, he couldn’t be in the house. Otherwise he’d squall. So he was always on the go. We’d pander to that, give him more and more opportunities. That’s middle-class parents for you."

Aged ten, Alistair decided independently that, to get better, he needed to get up early for a run before school every day and Keith insisted that he couldn’t go alone and that he should join him. Soon Keith started to sneak into Alistair’s bedroom when he had fallen asleep, to turn off his alarm clock. Not long after, Alistair started hiding the alarm clock.

From everything that we know about Alistair and Jonny, if there is anything innate, in-born that stands out, even from those days as a toddler, it is not excellence of performance at all, but a determination. 

When I first took Alistair to a crosscountry race, there were about 450 kids across all age spectrums. He came about 400th

In their races as juniors, they were good but not outstanding. In Alistair’s first triathlon, aged nine, he fell off his bike four times. He didn’t win but, more to the point, he made it to the finish. In his first 800m race, aged 12, for the Bingley Harriers, he came last. Their times, as younger teenagers, were so unexceptional that the Talent ID experts of today would not be impressed and would probably exclude them from any early junior elite training groups. This was in part because they suffered from the biological happenstance that affects many teenage athletes: they matured late. The other part was simply that they were not that naturally blessed.

According to Malcolm Brown, who has been their running coach since their early teens, "They weren’t the best talents in Britain in triathlon in that time. There were others better in their age group in the UK and definitely the world. They were good but they weren’t the best. They had races where they performed poorly. On measures of speed over 200m in the pool or 3,000m on the track, there were others who you would say were more talented athletes."

This is Jack Maitland, who has been their long-term swim coach: "They have great characteristics, but they are lacking in other areas. Like speed; neither of them was particularly fast. When they started with Malcolm, they were one-paced animals."

The boys themselves argue that maybe being slightly second-best in their junior years was instrumental. "I wonder about the thing about us not being that good," says Alistair. "Does that instil something in you? It doesn’t come easily, so you really have to work for it. It’s because you are not that physically mature, you don’t win things easily so you have to work for it – that carries on through. The guy that was physically mature and had more natural advantage, when he gets to 18, doesn’t have that natural advantage any more, and he hasn’t spent his years working and trying for it."

As Jonny says: "For some to whom it came too easily, they can get to the point where they realise: I don’t want to work for it." In other words, they didn’t care to nurture what gifts nature had given them. As for the Brownlees’ own gifts, the nurturing never stopped.

In one sense, they didn’t work for it, not work as in hard grind. But, almost without meaning to, they found themselves on a unique training programme. They cycled to school, Bradford Grammar, every day along a canal tow-path; that’s ten miles there and back, 40 minutes each way. Younger brother Ed went on the school bus and got the job of carrying their schoolbags. Then, at school, there happened to be a long-developed and well-coached running club, so they would go out running at lunchtime every day.

The school coach would put on races most weekends, they would also run for Bingley Harriers and, on top of all that, their absolute passion was competing in a series of fell races on the Brontë moors. Even to this day, they still insist on competing in the annual Auld Lang Syne race on New Year’s Eve – cold, wet, muddy – and they certainly never did it for the prizes; one of Alistair’s first trophies was a balloon-making kit. To this day, Dan Salcedo, one of their early triathlon coaches, says that the Auld Lang Syne race is, for the Brownlees, ‘their Disneyland’.

If you add to all that their swimming club (they both swam for their county) and the cycling club, which allowed them to join the regular long 100-mile Sunday rides into the Dales, you can see why the early advice from British Triathlon was: you are over-training. But they quite liked what they were doing, so they took on board the advice and ignored it.

They also thought nothing of defying the modern mores of child safety. Well, they were children, so they would, wouldn’t they? This is Keith on the subject, which he discusses with a faintly embarrassed giggle: "From a child protection angle, it is all a bit frightening. At 13, Alistair would disappear saying, 'I’m off for a ride.' I’d say, 'Where are you going?' He’d say, 'I don’t know.' 'Will you take a mobile phone?' 'No, it weighs too much.' Six hours later, he’d return after a 90km ride. I felt a lot more comfortable once they were doing it together."

Let’s cover off a couple more angles. Are they the product of pushy parenting? "We don’t think we are responsible," is Keith’s answer. "There is a very fine line between encouraging, facilitating, financing and pushing somebody. In all honesty, I think we were on the side of facilitating. I’ve had far more conversations with Alistair about reining it back, doing less, and I can’t think of any about doing more. Even now, I’d say the majority of conversations I have with him are: rest, don’t do as much."

And what is their response to being told to rein it in? "Like any teenage child to any parents, it’s 'You don’t know what you are talking about.' Al would say, 'You don’t understand. To be a professional athlete, you have to do the most you can to be the best you can.' He feels he knows better than I do. Remember, I am a medic, but he’s probably quite right."

There was one topic that parents and child debated hard: Alistair’s Cambridge University career. In 2006, the Beijing Olympics were a goal on a not-so-far-away horizon and yet his A-levels were good enough to win him a place to study medicine at Cambridge. Keith says: "I am absolutely of the opinion that children have to want to do what they do. If they don’t, they can always blame someone else. And they won’t commit." Nevertheless, on the subject of Cambridge, they were uncharacteristically firm. "His mother and I said, 'You have to give Cambridge a try, it is an opportunity you cannot say no to.' So the conclusion was: go to Cambridge, see if you can fit the training in around your studies. If it doesn’t work, reassess at Christmas."

So he went to Cambridge and his parents started receiving 5am phone calls saying: "I am running up the A14 on the hard shoulder." In other words, he had left the best training paddock in the world – the Yorkshire moors that were outside his front door – for a Cambridge A-road. "It just didn’t work," Keith says. "Wasn’t compatible. He saw his potential career diminishing." So, as planned, they reassessed at Christmas and Alistair left Cambridge.