Asher-Smith was more keen on hockey than sprinting when her coach John Blackie convinced her to dedicate herself to athletics; in her first race, she came fifth and only ran because a mate had promised her an ice cream if she ran.
Even once her talents for running had emerged and she had broken the 11-second barrier, there were still setbacks, major ones. She broke her foot a few months after Olympic relay bronze and had to have two screws inserted.
Johnson-Thompson has been lost too - at the World Championships in 2015, she was red-flagged three times in the long jump. She took nearly three minutes to complete the 800 metres, conserving energy for the individual long jump but forced to complete the event as pulling out injured would disqualify her from the whole meet. Then just 22 years old, Johnson-Thompson could not hide her disappointment. Glum didn't even begin to cover it. She even moved out of the team hotel in China because of the mistake that had seen her drop out of second place in the standings. Shame was the word she used.
Johnson-Thompson can be proud of her achievements now. The only reason she might have for moving out of the hotel this time is to stem the flow of endless well-wishers, keen to lay eyes on the golden girl. But she must also look to that dark day in the Bird's Nest for the roots of this victory. A year later, after finishing sixth at the Rio Olympics, she took herself away from the home comforts of Liverpool and moved to Montpelier. She became, in her words, more independent and decisive.
BEIJING, CHINA - AUGUST 23: Katarina Johnson-Thompson of Great Britain looks on before competing in the Women's Heptathlon 800 metres during day two of the 15th IAAF World Athletics Championships Beijing 2015 at Beijing National Stadium on August 23, 2015
Image credit: Getty Images
It shows too. Instead of looking focused and serious the whole time, a state of mind that must be exhausting to uphold for two days, Johnson-Thompson strolled around the stadium in Doha with a smile on her face most of the time, aided of course by three personal bests.
Smiling is something that comes naturally to Britain's other gold medalist. Asher-Smith is likely to challenge - but ultimately lose to Ben Stokes - in the BBC's popularity contest at the end of the year.
But her bubbly personality and infectious smile hide a steely determination.
"I train six days a week and I am still going to push myself to the limit. It’s very unglamorous when you’ve got lactic [acid], and you’re on the floor," Asher-Smith said after her 200m gold.
Sprinting is sometimes seen as the easiest event - it is the shortest after all - but Asher-Smith's 200m training involves plenty of 300m and 400m work, the distances Usain Bolt used to shy away from because there was too much hard work involved. The Brit studied history at KCL during her early career and prepared for these worlds with a part-time political philosophy course.
Asher-Smith's academic choices for next semester remain to be seen but her athletic ones are obvious: with two sprint medals in the bag and the potential for a third in the relays to come, she will run all three at the Tokyo Olympics.
Image credit: Getty Images
Elite athletes often talk about the difference between knowing and believing that you can do something, because sports psychologists have drummed into them how important it is to create a knowledge of being able to do something. Asher-Smith even alluded to it in her post-race interview. She knows she can double up now, something several top female sprinters did not do in Qatar because of the challenge involved.
Similarly, Johnson-Thompson always believed she could win world gold, but did not know it. Despite claiming, as athletes always do, that she would just do her best and what defending champion Nafissatou Thiam would be irrelevant, her defeat in the European Championships last summer would have been the seed of doubt in her mind.
In the end, it required both a career performance and a poor set of scores from Thiam to give the Brit her first global title.
That should not detract from the achievement though. Johnson-Thompson is performing at the levels of Jessica Ennis-Hill and beyond, and she is only getting better, having thrown personal bests in her two weakest events: the shot put and the javelin. Given the current trajectory, she will likely be favourite for Olympic gold when Tokyo comes around.
Between them, the Brits could come back from Japan next year with as many medals as surnames, grinning from ear to ear and teasing each other on social media, despite being from different ends of the country and living very different lives. Johnson-Thompson has moved away from her family who she admits did everything for her. Asher-Smith has had the same coach since she was eight years old.
For British sports fans, Olympic games tend to bring up memories of specific athletes: Daley Thompson in LA, Sally Gunnell in Barcelona, Steve Redgrave in Sydney, Amir Khan in Athens, the Super Saturday stars in London, even the GB hockey team in Rio.
Tokyo 2020 could forever be remembered as the year two British girls went to Japan athletes and came back heroes, fitting reward for a lifetime of hard work and sacrifice.