Katarina Johnson-Thompson's path to World Athletics Championships gold

Katarina Johnson-Thompson will now feel complete.

She has been among the best heptathletes in the world for several years and touted as a star of the discipline since winning the World Youth Championships a decade ago.

She has had an abundance of emotional support, ranging from her close bond with her mother - highlighted by a touching letter during the 2016 Olympics - to affection from friends such as Killing Eve actress Jodie Comer and athlete boyfriend Andrew Pozzi.

She has had UK Sport funding for most of her career and supplemented that with several commercial deals.

But there had been a major hole in her life, one that wasn't filled until a balmy night inside Doha's Khalifa Stadium.

That was when she comprehensively defeated defending champion and main rival Nafissatou Thiam to win heptathlon gold at the World Championships.

Johnson-Thompson triumphed in style with a British-record 6,981 points, beating silver medallist Thiam by 304 points and setting four personal bests in the process.

"She has slayed the dragon and banished the demons," Michael Johnson, a former world and Olympic 200m and 400m champion, told BBC Sport. "What you used to see between events was a worry that the demons are going to come back. She has now overcome that."

Her accession to the throne was expected to be faster and smoother, but there was to be plenty of heartache before she reached the top.

Having won the World Youth title in 2009, it was expected to be only a matter of time before she followed 2000 Olympic heptathlon champion Denise Lewis and eventually take over from Dame Jessica Ennis-Hill, who dominated the event from 2009 to 2015.

The perfect stepping stone to this seemed London 2012, for which she was selected alongside Ennis-Hill and Louise Hazel.

Actress Jodie Comer, who has just won an Emmy for her performance in Killing Eve, and Katarina Johnson-Thompson were classmates at St Julie's School in Liverpool

There were PBs in the 100m hurdles, high jump and 200m but she was last in the shot put and struggled in the javelin. At the age of 19, KJT - as she was starting to be affectionately known - had finished a very creditable 13th.

She said of the experience: "That stadium is always going to hold a special place in my heart and it definitely brings back a lot of emotions. In 2012 I was just going along with the wind really."

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Ennis-Hill, who has watched Johnson-Thompson since she was competing at youth level, told BBC Sport: "She's changed massively since those days of London 2012.

"She was relatively inexperienced, had fantastic raw talent, but hadn't understood how to put the events together."

The Liverpool-born athlete was starting to close the gap on Ennis-Hill and the rest in subsequent events. At the 2013 World Championships she came fifth and then won the traditional multi-eventers' Gotzis meeting in 2014 where a 19-year-old Thiam came fifth.

Just as she looked ready to make what seemed the natural move to a major global podium position, the incline started to get a little slippery.

Johnson-Thompson fell apart at the 2015 Worlds with three fouls in the long jump, having stood second after the first day behind eventual champion Ennis-Hill. Below-par performances in her Achilles heel events - shot put and javelin - then cost her a medal at the Rio Olympics in 2016.

"I remember doing the lap of honour with the girls in Rio and Kat was broken there, questioning whether she wanted to continue in the event," said Ennis-Hill.

That was Ennis-Hill's final appearance on the big stage as she signed off with silver, but looking down at her during the medal ceremony was Thiam - the athlete Johnson-Thompson comfortably defeated two years previously.

She decided to make a radical change, cutting ties with long-time coach Mike Holmes and joining Betrand Valcin in Montpellier, France.

In a revealing interview with the Telegraph after the 2016 Olympics, she said she had "not enjoyed anything in the past two years".

Ennis-Hill believes Johnson-Thompson's bold changes are what has helped her turn a big corner.

"Within the heptathlon it takes a long time to master all the events and then also bring them together in a championships," said Ennis-Hill.

"You will have disappointment and real setbacks but there comes an end point where everything eventually comes together.

"You can see she has grown massively in confidence having made huge changes by employing a new coach and moving to France."

A fairytale ending inside the Olympic Stadium - where it all began - at the London 2017 World Championships would have been fitting, but once again a major medal eluded her as she underperformed in the high jump with 1.80m. In the individual competition she managed 1.95m.

But the gods finally smiled on her last year. It started with the World Indoor pentathlon title, before Commonwealth Games gold and then the Europeans, where she finally gave Thiam a stiff test when taking silver.

It was the satisfaction of finishing only 57 points behind the Belgian, having also struggled with a calf problem, that gave her new-found confidence.

Johnson-Thompson was enjoying competing again, and said at the time: "This is definitely one of the favourite performances of my career, despite not winning."

She then set her target: "Thiam is the best female athlete in any sport. She's won Olympic, world and European titles and got over 7,000 points. I feel if I did all that I would want to, to be called the best in the world."

The big Liverpool FC supporter began to inch closer when she smashed her heptathlon personal best at Gotzis in May with a winning score of 6,813.

The elements now seemed in place for an assault on the world title; all she needed was to avoid mistakes and hope for some luck.

The brilliant personal best in the opening 100m hurdles on Wednesday was followed by an even better PB in the shot put.

Toni Minichiello, Ennis-Hill's former coach, told BBC Sport the "pivotal event" would be the javelin - and it proved to be.

Johnson threw another PB of 43.93m and Thiem, suffering from an elbow injury, failed to get the advantage needed over Johnson-Thompson going into the 800m. The Briton, knowing she had all but won gold, stayed relaxed in the final event before officially dethroning her rival.

Ennis-Hill added: "To come back and deliver in this way with all these personal bests is incredible.

"You have to get to the lowest point, the breaking point. She got to that and she made big changes and decisions and they are the reason she has gone on to improve and become world champion now.

"Once you win the first world title it gives you confidence and self-belief. It impacts how you perform in the next competitions and how people look at you.

"Thiam will fight back and fight harder at the Tokyo Olympics but Kat will have the massive edge she's never had before."

• Katarina Johnson-Thompson on Jodie Comer, sacrifices, and the south of France

'Amazing story for sport' - social media reaction

Ex-Liverpool defender Jamie Carragher: "Brilliant from Johnson-Thompson. World champion!"

Marathon world record holder Paula Radcliffe: "Utterly brilliant from Johnson-Thompson. So well deserved and a champion throughout."

Casualty actor George Rainsford: "Years ago I did a play at the Liverpool Playhouse and had a lovely dresser who had been a dancer called Tracy. She told me about her teenage daughter who was aiming to be a professional athlete. Well that girl was Katarina Johnson-Thompson and she is now a world champion!"

British high jumper Morgan Lake: "Two incredible days + a British record = World champion!"

Former pole vaulter Kate Rooney: "Amazing story for sport, learning from the past, making changes, perseverance and belief (and maybe a bit of hard work and talent thrown in there). Delighted for Johnson-Thompson."

Double Olympic champion Dame Kelly Holmes: "There you go...our newest world champion... awesome Johnson-Thompson!"