LONDON — When June Sarpong was 21 and an up-and-coming presenter on MTV in Britain, she walked past a newsstand and saw a magazine in its racks. On the cover was a story about successful women at the music station.

She grabbed a copy, only to discover she wasn’t featured. Sarpong — who is Black — hadn’t been asked to go along to the cover photo shoot with her white colleagues, even though she was the co-host of one of the station’s most successful shows. She wasn’t mentioned in the article.

“It was heartbreaking,” she recalled in a recent interview.

Soon, viewers noticed her absence too, and started calling MTV to ask why she had been left out. “It was this real teachable moment for the network,” Sarpong said.

Now 43, Sarpong is still trying to improve the diversity of British television — just at a much larger, and more politically fraught, level. In November 2019, she was named the BBC’s director of creative diversity, a high-profile role in which she is responsible for making Britain’s public broadcaster more representative of the country.

In recent months, she has announced her first policies to achieve that. Beginning in April, all new BBC television commissions will have to meet a target requiring 20 percent of jobs offscreen to be filled by people of color, disabled people or those from lower socioeconomic groups.

She has also secured 100 million pounds — about $136 million — of the BBC’s commissioning budget for new, diverse programming over three years. (The total commissioning budget is over £1 billion a year.)

At first glance, the BBC might already seem to be making strides. Some of its biggest shows last year were led by and focused on people of color, such as Michaela Coel’s “I May Destroy You,” about a Black woman confronting hazy memories of a rape, and Steve McQueen’s “Small Axe” series of films about Black British history. The BBC has also beaten an internal target, set before Sarpong took up her job, for people of color to make up 15 percent of its on-air talent.

Away from the spotlight, however, Sarpong said, the picture was far less encouraging. Last month, Sarpong issued her first major report in her new role, highlighting some of the challenges ahead.

“The BBC has been incredibly successful in terms of what you see,” she said, “but in terms of below the line, behind the camera, certainly not.”

The job also places Sarpong at the center of a political battlefield. The BBC is funded by a compulsory license fee for all television owners, and, though less ubiquitous than it once was, the corporation plays an enormous role in national life, with dominance in everything from online news to toddler cartoons to orchestral music. The average British person spends well over two hours a day with BBC output, according to an estimate by an official regulator.

It is also, increasingly, a political punching bag. Over the past year, conservative politicians have repeatedly criticized the organization, claiming that it was promoting a “woke agenda,” including when it proposed omitting the lyrics to jingoistic songs traditionally performed at an annual classical concert.

Left-wing commentators have been equally critical, especially when a story emerged claiming that the broadcaster had barred employees from attending Black Lives Matter protests or Pride marches. (The BBC said its rules had been misinterpreted.).

Sarpong said she’d gotten “a few more gray hairs since starting” her role, but added, “Whatever criticism I get is worth it, as there’s a bigger mission here.”

Sarpong was born in east London to Ghanaian parents. She spent her early years in Ghana, until a coup forced her parents to flee back to London, where she lived in public housing.

As a teenager, she was involved in a car accident that left her unable to walk for two years, she said. While she was in the hospital, she watched Oprah Winfrey on television and it made her realize she could work in TV, she added. Her school reports had always said she “must talk less,” Sarpong said. “I remember watching Oprah thinking, ‘Oh my God, you can be paid to talk!”

Sarpong soon got an internship at Kiss FM, a radio station specializing in dance music. She turned up wearing a neck brace, and recalled what it was like to have to explain her accident to every person she met.

Her rise from that small role, then MTV, was swift. Sarpong became a youth TV star in Britain after moving to a more mainstream network, Channel 4, where she presented a popular weekend show and interviewed the likes of Kanye West and Prime Minister Tony Blair. She was known especially for her laugh — “An irresistible elastic giggle,” according to The Guardian.

But she hit problems when she tried to move further up the TV ladder, she said. She went to meetings about “shiny-floor shows,” a reference to big Saturday-night entertainment programs, but was told their audiences weren’t ready for a Black host, she said. She moved to America, and, increasingly, into activism.

Friends and acquaintances of Sarpong said in telephone interviews that she has the character to change the BBC. “They’ve actually hired an attack-dog who will not let go,” said Trevor Phillips, a former TV news anchor who was also the chairman of Britain’s Equality and Human Rights Commission, in a telephone interview.

Lorna Clarke, the BBC executive in charge of its pop music output, described her as charming, but firm. “I’ve seen her in action here and it is impressive,” she added. “She’s there saying, ‘We can do this, can’t we?’”

Some of the BBC’s critics say the most alarming area in which the corporation lacks diversity is not in terms of race, sexuality or disability, but in the political outlook of its staff. Ministers in Britain’s Conservative government, and others on the right, have used the language of diversity in criticizing what they claim is the BBC’s liberal bias, with the culture secretary, Oliver Dowden, saying the broadcaster needed to do more to reflect “genuine diversity of thought.”

Simon Evans, a self-described right-leaning comedian who sometimes appears on BBC radio shows, said in a telephone interview that the BBC’s comedy output was dominated by left-wing views. “You have to get people in who have diversity of opinion, and views, and skin color as well,” Evans said. “That will crack the ice cap over the culture of the organization,” he added.

Sarpong said diversity of opinion at the BBC would increase if her policies succeeded. “If we’re doing our job, you will have that,” she added.

Sarpong has mingled with stars throughout her career, but she said she’d also gone to every corner of Britain while making TV shows. She knew what made the British people tick, she said, and that would help her succeed. “You’ve got to be looking at how to bring the majority along with you,” she said, and convince them that diversity isn’t a zero-sum game where one group benefits at the expense of others.

“Everybody has their role to play, and it’s very important to know what your role is,” Sarpong said. “I’m very clear about what mine is.”