Katarina Johnson-Thompson’s heptathlon dream was torn apart in Tokyo as her right calf gave way while she was surging towards medal contention. But, even on one of the most painful and despairing nights of her career, her Olympic spirit remained undiminished.

First the 28-year-old hopped on her left foot a dozen times, before flopping to the floor. Then, as the tears began to flow, she covered her eyes and took refuge in the dark. But when a wheelchair was rolled out, she was determined to go out on her feet.

It took a while. And there were echoes of Derek Redmond at the 1992 Barcelona Games as, slowly and bravely, she moved towards the finish line of the 200m.

Every step looked more tortuous than the last, but she got there. Yet when she did, after the longest 93 seconds of her life, insult was added to injury as she was disqualified for going out of her lane. It was a heartbreaking end to what until then had been an unexpectedly heartwarming day.

“I am so gutted for her,” said Denise Lewis, the 2000 Olympic heptathlon champion, who has been a guiding voice to Johnson-Thompson. “She has worked so hard to get to this stage. Someone’s heart has been trashed on the track. It will be hard for her to come back from this emotionally – but she will.”

Not much had been expected of Johnson-Thompson in her first major competition since rupturing an achilles tendon in her left leg in December. Instead, with the smell of glory in her nostrils, the reigning world champion surprised us all.

A vibrantly strong challenge began with her running her second fastest ever 100m hurdles in 13.27sec, scoring her 1,084 points and putting her 40 clear of the big favourite Nafi Thiam of Belgium.

A reasonable high jump of 1.86m – albeit 12cm below her best – kept her in the hunt before an excellent shot put of 13.31m, the second best of her life, reinforced the fact that she was a genuine contender.

That was if her body could hold up. The fact her legs were strapped up and she was receiving treatment suggested it wasn’t a given, and the London 2012 long jump champion Greg Rutherford had noticed early on that something was not quite right.

“I was having conversations with people after she’d done her morning session, and you could see that there were a few issues there, she looked like she was limping a bit off of the high jump,” said the Eurosport commentator and Guardian columnist. “But again we just got a couple of words as she came through, just asking if she was OK. It was a tentative ‘yes’, and you obviously have to go with the athlete when they say that, but clearly it wasn’t to be.”

Johnson-Thompson was fifth in the standings at the start of the 200m, but the way she powered around the bend suggested she would be in silver or bronze medal position overnight – until her hopes and her calf were torn apart.

It meant at the end of day one the Dutch athlete Anouk Vetter led on 3,969 points, with the Belgium Noor Vidts second on 3,941 and Thiam in the bronze medal position. Meanwhile, Johnson-Thompson – just as at the 2015 World Championships when she fouled three times in the long jump while in gold medal contention – was left picking up the pieces.

It was the latest bad-luck story to befall Britain’s athletes in these Games with Dina Asher-Smith and Adam Gemili having suffered injuries either in the buildup or during the Games. There was better news for Britain as Jodie Williams produced the performance of her career to break the 50-second barrier for the first time by running 49.97 to move into the 400m final.

“It’s crazy because three weeks ago I broke 51 seconds for the first time,” she said. “I saw all of those girls go 49sec in the first heat and I was like: ‘You have no choice now’ and I ran for my life,” said Williams, who has had more than her share of injury worries. “I’m so happy. It began sinking in when I was walking just then and I started crying. It’s been such a long journey but in that final anything can happen.”

Elsewhere Laura Muir qualified for Friday’s 1500m final by finishing second to Sifan Hassan, whose historic treble attempt lives on, while Andy Pozzi made the 110m hurdles final as a fastest loser.

Peruth Chemutai became the first Ugandan woman to win an Olympic gold medal in any sport when she became a surprise winner of the women’s 3,000m steeplechase. The 22-year-old clocked a time of 9min 01.45sec to finish over three seconds ahead of American silver medallist Courtney Frerichs with Kenya’s Hyvin Kiyeng taking the bronze.

“I’m so happy and proud of myself. It was a good race – I enjoyed myself and I enjoyed the weather,” Chemutai said as she joined John Akii-Bua’s 400m hurdles win in 1972 and Stephen Kiprotich’s victory in the 2012 marathon as Uganda’s Olympic victories.

There was a shock in the men’s 800m as Emmanuel held off his more fancied compatriot Ferguson Rotich in a slow final that was won in 1min 45:06sec.