Nicola Adams’s skill and sunny outlook lit up an often acrid boxing world | Kevin Mitchell

Interviewing Nicola Adams could be an unnerving experience. As her eyes sparkled, sweat dripping from a face seemingly too innocent for fighting, she would further illuminate the occasion with a smile that could light up a funeral on a winter’s day. It did not matter the result (although she never lost in 14 amateur and six professional contests), so searching for disappointment or joy led inquisitors down the same route. It was as if she had been sent to destroy all notions of what a fighter should be.

When Adams was due to make her Las Vegas debut in 2017, on the undercard of the world title fight between Saúl Álvarez and Gennady Golovkin, her opponent, Alexandra Vlaik, had to withdraw an hour before the bout because of an irregular blood test. Yes, Adams said, she was, “devastated”. But she did not complain about her opponent or her own misfortune. Instead, her instinct was to be grateful for an opportunity that did not even materialise.

“Thank you everyone for your support and kind messages,” she said, before taking her seat at ringside. It was the most curious response, the hard-nosed local fight writers reckoned. But those who had witnessed her career at close quarters were not surprised.

Adams, who has had to retire from boxing at 37 because of fears that she is risking permanent damage to an eye, beguiled a nation with her unalloyed decency – and will continue to do so in whatever career she pursues, from acting (she has worked as an extra on Coronation Street, Emmerdale and EastEnders) to the media.

She was born in Leeds, worked in Leeds (as a builder) and, after boxing in London, lived in Leeds, so it was fitting she chose the Yorkshire Evening Post to announce she was leaving the sport.

“Having people in my life who are a fountain of support, kindness and love,” she said on Wednesday, “has been the sole reason I’ve been able to represent my country in the way I have.”

For Adams, boxing was always an obligation as well as a privilege and, when she sensed victory, a pleasure. Few fighters had such a highly developed sense of duty to please her fans and her compatriots. But she was no soft touch once the bell went. Adams had the easy knack of ruining the evening of many an opponent with fists that must have felt like hammers. She could hit and hurt.

Nicola Adams v Maria Salinas

Nicola Adams lands a punch on María Salinas at the Royal Albert Hall in her final professional bout. Photograph: Philip Sharkey/TGS Photo/Shutterstock

Like most boxers, the real Nicola Adams was not someone who recognised other people’s perceptions of her, inside or outside the ring. Fighting was what she was good at, what she did for a living; being friendly, cooperative and patient is who she was.

Often, she surprised herself. “It’s still sinking in,” she said after winning her first Olympic gold medal, in London seven years ago. “It’s a childhood dream come true.” Humility underpinned her public pronouncements, although there she did not lack for self-belief or commitment in a sport where those qualities can be easily drained.

If she spoke in well-worn cliches, her sentiments were heartfelt. “I didn’t realise it was such an exciting fight until I watched it back,” she told an admiring Gary Lineker after winning her gold medal against Ren Cancan in 2012. “You were so strong,” he said, “kept going and kept going. You battered her.”

Lineker, no stranger to praise in his football career, echoed the thoughts of a nation. People unfamiliar with Adams and her sport struggled to comprehend how someone so gentle and content could inflict pain with the same ruthless single-mindedness as her male counterparts. When she defended her Olympic title in Rio in 2016 (the first British boxer to do so in 92 years), her reputation as a smiling assassin was assured.

Had she chosen to continue boxing, Adams might have gone on to dominate her division all the way to Tokyo next summer.

Her priorities shifted in 2017. She had to earn a living, and promoters circled eagerly when it was obvious she was going to cash in on her gifts while she was still able, at 35. She had only six paid fights – the last of them at the Royal Albert Hall in September, a grinding defence of her WBO world title against the seasoned Mexican challenger, Maria Salinas. There was little in it over 10 rounds, Adams relieved as much as elated to retain her title with a split draw.

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Adams left the amateurs more garlanded than any boxer of her era: the first British woman to win a European title, a Commonwealth champion as well, the first to win a medal at the world championships, the first woman to win an Olympic gold medal in her sport – and then to do it again. She was also the first openly LGBT fighter to win Olympic gold. Wherever she went she made history and spread feelgood warmth rare in a business that too often is mired in acrid conflict.

As her promoter, Frank Warren, observed with pride: “Nicola has that star quality in abundance that very few possess.”

It took Andy Murray’s grand slam breakthrough and Olympic gold medal to stop her winning the BBC’s Sports Personality of the Year award in 2012. And she never did get her chance to fight in Vegas. But Adams has so many gilded memories to cherish none of that will bother her. Nothing does, it seems. And that is her real genius.