LONDON - The bungling of reports that powerful Britons sexually abused children has thrown one of the largest and most respected broadcasters in the world into a deep crisis.

It is hard to overstate the importance of the BBC in British society; its influence stretches throughout the former British empire and beyond. Over the years, the BBC has been behind almost all of the U.K.'s broadcast milestones, serving as a voice for the British nation. Its airwaves have carried the clanging of Big Ben's bells, wartime messages from Winston Churchill, and the music of the Beatles — exporting British culture to a global audience.

The head of the BBC's governing body called Sunday for an overhaul of the broadcaster. That could mean many things for the sprawling organization that has long emphasized its obligations to the public. To know what it would take, it is important to know what the BBC is and the scale of the crisis it faces.

WHAT HAPPENED:

Last month, the BBC drew fire after it emerged its "Newsnight" program had shelved an investigation into child sexual abuse allegations against Jimmy Savile, the broadcaster's renowned TV host who died last year.

Police say that since their investigation started they have received complaints from some 300 victims of the platinum-haired, tracksuit-wearing Savile and associates — and that some of the abuse may have occurred on BBC premises. Questions soon arose over whether shelving the "Newsnight" piece was part of a coverup or if BBC managers had heard of but ignored claims of abuse by Savile while he was hosting such shows as "Top of the Pops."

Amid public outrage, BBC director general George Entwistle announced internal inquiries into why the "Newsnight" investigation was canned as well as the BBC's "culture and practices" during the years Savile worked there.

But then, "Newsnight" wrongly implicated a British politician in a sex-abuse claims program that aired Nov. 2.

The BBC didn't name the alleged abuser, but online rumours focused on Alistair McAlpine, a Conservative Party member. On Friday, McAlpine issued a fierce denial, and shortly after, the abuse victim interviewed by "Newsnight" admitted he had mistakenly identified his abuser.

The BBC apologized for airing the program, which Entwistle said he had not been made aware of. That stance drew incredulity from politicians and media watchers wondering if he was out of touch or inept. The criticism reached fever pitch, and Entwistle decided to resign Saturday. A day later, Chris Patten, the head of the BBC's governing body, called for a "thorough, radical structural overhaul" of the broadcaster.

THE BBC'S EVOLUTION

Some observers say the BBC's massive size and rapid growth have resulted in a decentralized structure without clear lines of responsibility, leaving the door open for shoddy journalism. But while today the BBC is a global brand, it started out with a simple mission in November 1922: to inform, educate and entertain.

It took on a crucial role in public life with the onset of World War II, when the service brought Churchill's famous speeches to the airwaves. The BBC expanded its overseas language services, and its radio programs became a lifeline of information — including even for Nazi leader Adolf Hitler's own command, according to the broadcaster.

Television took on a greater role within the organization after the war, hitting a milestone when 20 million viewers tuned in for Queen Elizabeth II's coronation in 1953. The BBC expanded its offerings, launching current affairs program "Panorama" — still a hit today — and the first British soap opera.

The media behemoth's solid news foundation showed in the 1980s with its coverage of the Falklands War, the first Live Aid concert and the royal wedding of Prince Charles and Diana, which drew one of the largest TV audiences ever.

In more recent years, the BBC has greatly expanded its digital broadcasting and Internet services.

HOW BIG IS IT?

Today, the organization says it reaches a weekly audience of 166 million people globally over multiple platforms, including radio, digital satellite and cable channels.

The BBC boasts 10 national TV channels in addition to regional U.K. programming, 10 national radio stations, 40 local radio stations and a website which averages 3.6 billion hits a month.

The BBC World Service broadcasts globally on radio, TV and online, providing news and information in almost 30 languages. The broader organization, meanwhile, cranks out TV gold such as science fiction series "Doctor Who" and long-running soap "EastEnders."

Its commercial arm, BBC World News, broadcasts 24 hours a day in more than 200 countries and territories.

HOW DOES IT DO IT — AND AT WHAT COST?

Most of the BBC's services in the U.K. are funded by a tax on households that have televisions or watch TV on computers or other devices, while profits from commercial ventures such as BBC Worldwide and BBC World News are used to invest in new programming and services.

Still, rival broadcasters in the past have complained that the BBC has used public money to fund types of programs supplied by commercial operators, ditching its public service mission in a quest for viewers.

Under pressure from critics to justify its 3.5 billion pound ($5.6 billion) budget in a time of austerity, the BBC in recent years has undergone a series of job cuts, cuts to operations and unpopular changes to employee pension programs.

Most of those changes were ushered in by Mark Thompson, who preceded Entwistle as BBC director general. Thompson is to assume the role of chief executive of The New York Times Co. on Monday, but faces questions over the BBC's decision to kill the "Newsnight" program on Savile — which occurred while he was still in charge.

PAST BBC CHALLENGES

The BBC has repeatedly faced off against the government over editorial independence.

Its first major confrontation was during the 1926 general strike, when Churchill unsuccessfully lobbied the prime minister to commandeer the airwaves because the strike limited the modes of communication between the government and the public.

The BBC later came under pressure to support a campaign in the Falklands in 1982, enraging the Margaret Thatcher government by casting doubt on official sources. The BBC's director general at the time insisted it needed to "guard its reputation for telling the truth."

In 2003, a BBC reporter suggested that then-Prime Minister Tony Blair had misled parliament with claims that Iraq had weapons of mass destruction. The government called for an apology, but the BBC refused. The BBC's source, weapons expert David Kelly, was named in the media and had to explain himself repeatedly. He later killed himself.

The inquiry into Kelly's death said the reporter had made "unfounded allegations" and called the broadcaster's editorial processes defective. The inquiry's findings led to the resignations of the BBC's chairman Gavyn Davies and its director-general, Greg Dyke — and the installation of Thompson as successor.

WHAT'S NEXT?

The broadcaster's charter sets out that "trust is at the foundation of the BBC: we are independent, impartial and honest." But public trust in the BBC has been declining for decades, according to polls, and the latest scandals are unlikely to help.

Entwistle may have quit, but observers say the BBC Trust, which ensures the broadcaster stays true to its public obligations, deserves scrutiny, too. Patten is expected on Monday to lay out plans for how to deal with the aftermath, and many expect more BBC resignations as the fallout spreads.

Kevin Marsh, a former senior BBC editor, says the broadcaster needs to get better at explaining itself and admitting its errors. Even if it never fully recovers, the BBC can probably "learn to live with" a new reality of weaker public confidence, he added.

Tim Davies, a former PepsiCo executive with a marketing background and no experience as a journalist, has been named acting director general. While BBC insiders might regard Davies with suspicion, "He doesn't have BBC blood flowing through his veins, and quite honestly at the moment that could be an advantage," Marsh said.

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Associated Press writer Cassandra Vinograd can be reached at http://twitter.com/CassVinograd

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