Johnson-Thompson produced the fourth-best first day in heptathlon history on Wednesday, setting personal bests in the 100m hurdles and shot put to lead defending champion Thiam by 96 points with three events remaining.
The Liverpudlian had demons to banish at the World Athletics Championships after four years ago in China where she failed to record a legal long jump but was forced to complete all seven events so she would still be allowed to compete in the individual high jump.
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The memory of her effectively being forced to jog an 800m race in a time that was 40 seconds slower than her personal best would have been well to the back of her mind as she arrived at the final event this time around with a buffer of as much as six seconds over defending champion Thiam.
Expectation was higher this time around for the reigning world indoor pentathlon and Commonwealth heptathlon champion, who finished second to Thiam in their last major championship clash - the Europeans in Berlin last summer.
Katarina Johnson-Thompson awaits her long jump mark
Image credit: Getty Images
The penultimate event - the javelin - is traditionally a weakness of Johnson-Thompson while her rival Thiam excels in the power event.
However, Johnson-Thompson produced her third personal best of the World Championships - throwing 101 centimetres further than she ever has before - to minimise the damage of Thiam's powerful performance.
It meant Johnson-Thompson could have lost to Thiam by as much as six seconds in the 800m and still been sure of securing a historic world title.
But she did anything but, running a personal best of 2:07.26, her fourth of the week, and breaking Jessica Ennis-Hill's British record by finishing with a total of 6,981 points.
"It doesn't make sense to me," Johnson-Thompson said.
"These whole two days have been so fast and because it's been at night and the lights, it's actually been like a dream!"