On Friday 11 February, thousands of Arabs spilled on to the streets of the Middle East's capitals, from Rabat to Amman, to celebrate the downfall of the Egyptian dictator Hosni Mubarak. Doha, in the sleepy Gulf emirate of Qatar, was no different: hundreds of youths brought traffic to a standstill on the coastal ­Corniche Road. Shortly before midnight, some of them recognised one of the drivers stuck in the jam: the then Al Jazeera director general, Wadah Khanfar, who was on his way home from the network's headquarters to grab a few hours sleep. After pulling him out of his car, dozens of Qataris queued up to hug and kiss him and thank him for his channel's unrelenting, round-the-clock coverage of the uprisings in Cairo and Tunis.

“I wept," recalls Khanfar, seven months later, when I meet him in the café of a central-London hotel. "I was very emotional." He pauses. "In the Arab world, journalism ­really is an issue of life and death."

He isn't exaggerating. So far this year, Al Jazeera's correspondents and producers across the Middle East have been harassed, arrested, beaten and, in the case of the cameraman Ali Hassan al-Jaber, killed (by pro-Gaddafi fighters in Libya). As Arab governments toppled from Tunisia to Egypt to Libya - and, last month, Yemen - Al Jazeera has been on hand to beam the pictures of ecstatic protesters, revolutionaries and rebels into the living rooms of ordinary Arabs across the region - and beyond. In Tunisia, the network picked up camera-phone footage from Facebook and other social-networking sites of the riots and protests that took place in the wake of the fruit-seller Mohamed Bouazizi's self-immolation in December 2010, and gave them a regional prominence they otherwise would not have achieved.

In Egypt, for 18 days straight, Al Jazeera's cameras broadcast live from Cairo's Tahrir Square, giving a platform to the demonstrators, while documenting the violence of the Mu­ba­rak regime and its supporters.

“The protests rocking the Arab world this week have one thread uniting them: Al Jazeera," the New York Times observed on 27 January, as it reported on how the channel's coverage had "helped propel insurgent emotions from one capital to the next". "They did not cause these events," argued Marc Lynch, a professor of Middle East studies at George Washington University, "but it's almost impossible to imagine all this happening without Al Jazeera." Or, as a spokesman for WikiLeaks tweeted: "Yes, we may have helped Tunisia, Egypt. But let us not forget the elephant in the room: Al Jazeera + sat dishes."

At 45, Khanfar, a tall, bearded, elegantly dressed Palestinian, oozes charisma. A former reporter and analyst at the network, who rose rapidly through the ranks to become director general in 2004 at the age of 37, he has since featured in Time's annual list of the 100 most influential people in the world and Forbes's annual list of the world's most powerful people.

Khanfar describes Al Jazeera - which means "the island" - as a "phenomenon". "When it was established, in 1996, it was an exception within the Arab media landscape," he says. "By 2001, Al Jazeera was a well-established voice in the region and even internationally, because of the war in Afghanistan and the fact Al Jazeera was the only broadcaster covering the story from inside Afghanistan."

However, it has been the events of 2011, more than 2001, that have come to define the broadcaster and which have made politicians, journalists, and above all viewers, sit up and take notice of Al Jazeera and its output.

So does Khanfar believe that Al Jazeera was a driving force behind the Arab spring? He won't describe the network as a "cause" of the protests but he admits that it "magnified [protesters'] voices and made them mainstream". For example, Mubarak, he says, "used to tell the parents, 'Go down to Tahrir Square, collect your kids'. But when the parents saw what their kids were doing on Al Jazeera, it became mainstream and they joined them." Yes, but would the revolts have happened without Al Jazeera? Khanfar hesitates. "It would have happened, yes, but it would have maybe been much more expensive [in terms of lives lost] and would have taken much longer to accomplish."

In September, however, despite having presided over the most high-profile, high-impact year in the network's history, Khanfar resigned, suddenly and without warning. ­Rumours continue to swirl as to whether he jumped or was pushed but the fact that his ­replacement, Sheikh Ahmed bin Jassim al-Thani, is a member of the Qatari royal family, with no background in journalism, has left some supporters fearing what the future holds. Al Jazeera, it seems, is at a crossroads.

I arrive in Doha, on a visit organised by Al Jazeera, and am greeted with a wall of hot air as I disembark from the plane. Qatar occupies a small peninsula on the north-eastern coast of the Arabian Peninsula - so small that most foreign maps drawn up prior to the 19th century didn't show it. Flat as a pancake, the country's sole land border is with Saudi Arabia to the south, while the rest of its territory is surrounded by the Persian Gulf.

Like Saudi Arabia, Qatar adheres to the puritanical Wahhabi school of Islam, although Qa­taris tend to not practise it as strictly as their Saudi cousins. There is, for example, no legal requirement for women to wear a face veil or even a headscarf. Within minutes of leaving Doha International Airport, I can't help but notice a semi-naked Rosie Huntington-Whiteley staring out from a Burberry billboard ad.

Distances are short in Doha. Driving from the airport to my hotel and then on to the Al Jazeera headquarters, you see how tiny the thumb-shaped emirate is. Both in terms of people (1.7 million) and size (11,500 square kilometres), Qatar is smaller than Northern Ireland. And, of those 1.7 million residents, Qatari citizens make up just one in seven, or 250,000 - a population that would struggle to fill one of Cairo or Baghdad's larger neighbourhoods. The majority are migrant workers, predominantly from the Indian subcontinent.

But what Qatar lacks in size, it makes up for in money. It sits on the third-largest natural gas reserves in the world and, in 2010, according to figures compiled by the IMF, it surpassed Luxembourg to become the world's richest nation, with a per capita income of $88,000 - almost twice that of the US.

The Qatari economy is booming: growth stands at an astounding 19 per cent and cranes dot Doha's skyline; every building I pass - even the mosques - looks brand new.

It is ironic that a television news network famed for democratising and opening up a region scarred by tyranny and despotism is based here in Doha. Qatar, after all, has long been an absolute monarchy. Its emir, Sheikh Hamad bin Khalifa al-Thani, seized power from his ­father in a peaceful palace coup in 1995; the al-Thani family has been ruling Qatar since 1825. But the emir, a tall, corpulent man whose girth was once mocked by Colonel Gaddafi, has transformed Qatar's image and level of influence on the international stage. In recent years, Qatar has donated hundreds of millions of dollars to the US victims of Hurricane Katrina; bolstered the peace process in Darfur; brokered a deal between rival Lebanese militias; and helped reduce tribal tensions in Yemen. Most recently, Qatar threw its weight behind the Egyptian protesters against Mubarak and then pushed for military action against Gaddafi's Libya, providing funding for the rebels and even military aircraft for the Nato-led bombing campaign - the only Arab state to do so.

It has been at the forefront of the Arab League's efforts to sanction and isolate Syria and has tried, in the words of Khaled Hroub of Cambridge University's Gulf Research Centre, "to wrest control from regional third parties, such as the Saudis" and "fill a regional leadership vacuum". Is it any wonder then that a recent headline in the Economist dubbed the bantam-sized emirate a "pygmy with the punch of a giant"?

It is Al Jazeera - the network founded by al-Thani in November 1996 and bankrolled by him ever since - more than any other single ­factor, that has empowered Qatar and boosted its reputation. According to the Qatari media ­consultant Hassan Rasheed, the broadcaster is "Qatar's passport to the world". At a seminar to celebrate "Al Jazeera at Fifteen Years" that I attend at Doha's Sheraton hotel, Philip Seib of the University of Southern California and author of the forthcoming book The Al Jazeera Effect and Real-Time Diplomacy, says the network helped Qataris "put their country on the map". Members of the audience nod ­furiously. Seib then points out how Al Jazeera was a "public diplomacy creation . . . probably one of the most successful in history". The Al Jazeera representative on the panel suddenly looks distinctly uncomfortable.

Al Jazeera is plagued by accusations of bias. But, to the network's credit, they come from all sides: Islamists, secularists, dictators, democrats, Sunnis, Shias, Israelis, Americans - none can decide for sure whether the network is friend or foe.

Take Israel. Al Jazeera is often accused of being hostile to the Jewish state and one-sided in its coverage of issues such as the Gaza blockade; yet it was Al Jazeera that became the first Arab broadcaster to offer a voice to Israeli officials (often speaking in Hebrew!). In his 2005 book, Al Jazeera: The Inside Story of the Arab News Channel That Is Challenging the West, the British journalist Hugh Miles wrote about how the interviews with Israeli army officers and military spokesmen were "truly shocking for the Arab public", especially because "many Arabs had never seen an Israeli speak before". (Khanfar tells me viewers used to phone in regularly to complain about the presence of "lying" Israeli officials on the channel.)

Whether you are for or against Al Jazeera, its power, influence and reach cannot be disputed. From the very beginning of the protests in Egypt, the Mubarak regime recognised it as a threat, revoking its licence to broadcast, ransacking its Cairo bureau and trying to take it off air. The network had to stop naming its correspondents and producers on the ground in Egypt for their own safety. Meanwhile, demonstrators in Tahrir Square could be heard chanting: "Long live Al Jazeera!"

“All this noise from such a small matchbox," a startled Hosni Mubarak is said to have remarked on a visit to the Al Jazeera headquarters in Doha a few years ago. Little did the ageing tyrant realise how much damage this matchbox would do to his regime.

The headquarters consist of two nondescript buildings adjacent to one another: on the right, Al Jazeera Arabic, on the left, Al Jazeera English, which has been broadcasting since 2006. The security is intense: I have to navigate two checkpoints, providing ID and letters of invitation at each, as suspicious guards look me up and down.

Inside, it is a different story. I worked at Sky News as a producer and programme editor ­between 2005 and 2007, and I remember its Osterley studio in west London being a hive of ­frenetic activity: producers running across the newsroom, news editors barking orders to reporters on the phone, "breaking news" straps ready to go. By comparison, the sky-blue Al Jazeera English newsroom in Doha is ­sedate. There is no running and the staff - representing more than 40 nationalities (but with Brits and Americans perhaps over-represented) - seem to be a calm and deliberative bunch.

Al Jazeera English broadcasts to around 250 million households in 130 countries, not far off the global reach of its main rivals, CNN and BBC World. Al Jazeera Arabic, by contrast, reaches 70 million households, mostly in the Middle East and North Africa. Between them, the two news networks employ more than a thousand staff and have 70 foreign bureaux.

I meet Al Anstey, a 45-year-old former ITN journalist who was appointed managing director of the English channel in October 2010, in his vast corner office. Sitting on a cream leather couch, his arms spread out, Anstey exudes confidence. Tall and well-built, he is wearing a dark-blue suit, his crisp white shirt open at the neck. Above his head hang four flatscreen TVs, each airing a different international news channel. "If you look at our competitors, they see the world through the prism of where they are centered," argues Anstey, nodding at the screens above him. "So CNN, with its headquarters in Atlanta, will see the world through a more American prism; the BBC sees it through a more European prism." He says Al Jazeera is different: "It covers the developing world as well as the developed world; it gives voice to disenfranchised and neglected peoples."

So it's a pan-Arab channel? "No, we see ­ourselves as a global channel," says Anstey, who has been with Al Jazeera English since it launched five years ago. "We have been extremely strong covering the Arab spring. But we were also extremely strong on the Japanese earthquake." Others at the channel seem less defensive. "I think it's critical that we keep that sensibility, that we are a Middle Eastern channel," says Mike Hannah, a South-African-born correspondent who worked for CNN as its Jerusalem bureau chief before he moved to Doha. "I think that if we lose that, we lose our specific identity."

I ask Anstey what I asked Khanfar: did Al Jazeera help cause the Arab spring? He is adamant that his channel was not behind the recent revolutions and upheavals in the region. In the past he has said Al Jazeera is "categorically anti-nothing and pro-nothing". Now he says: "The simple answer is we covered the Arab spring; we didn't create it."

Again, Hannah goes further: having acknowledged the role that Facebook and Twitter played in spurring on the protests in Tunisia and Egypt, he reminds me that it was Al Jazeera that provided the "glue" - visually and editorially - to hold it all together: "The Arabic and English channels provided the bridges that allowed people to connect with each other."

After my meetings with Anstey and Hannah, I walk over to the next-door building to see Mustafa Souag, managing director of the Arab channel, who says he has "15 minutes only" to speak to me in his tiny, cramped, ­windowless office. Dressed in a crumpled khaki suit, this Algerian intellectual is a former professor of literary theory, who once lived in London and worked for the BBC. He says his "proudest" moment at the network was when he was told by his reporters in Cairo that government sources credited the presence of Al Jazeera cameras with preventing a massacre of protesters by Mubarak's camel-riding thugs in Tahrir Square.

Souag's take on the Arab spring is distinctive: he argues that the real impact of the network was on Arab opinion in the years running up to 2011: "We provided Arab citizens with knowledge and information, [political] positions and ideas . . . when you give people the right information you empower them." But empower them in which direction? Al Jazeera's secular critics, for example, see it as a platform for Islamist parties, whom they claim are over-represented on the channel's output.

Souag, after denying that the channel acts as a showcase for "extremists", reminds me that "90 per cent of our audience are Muslims and they need to hear from these people" - that is, the Islamists. But he rejects the charge of being biased in favour of groups such as Hamas in Gaza or the Muslim Brotherhood in Egypt: “I have asked our quality control to go through our output for the whole week and give me specific examples of imbalances, and each time I do so they come back and show me that we haven't been biased and, often, the Islamists have been given even less time than the non-­Islamists." (Back in London, Khanfar is more willing to engage with the critique: "There are too many Islamists on the screen not because of an editorial decision or an editorial bias but ­because Islamists right now are the most influential [movement] in Arab society.")

Then there is the network's relationship with its host nation. It is rare to see Al Jazeera - either the Arabic or the English channel - critically covering the Qatari regime or human-rights abuses inside the emirate. As a US state department cable released by Wiki­Leaks pointed out, Qatari officials "view AJ, both English and Arabic, as important tools of Qatari foreign policy". Another cable adds: "Al Jazeera has resolutely steered away from . . . reporting on anything politically controversial in Qatar."

I ask Anstey how often he is rung up by members of the ruling family: "never". He doesn't budge: "We are not a mouthpiece [for Qatar]; we are not a tool of public diplomacy. We have come here as journalists to carry out the profession of journalism."

He won't, however, tell me how much money the emir provides the network with - but Abderrahim Foukara, Washington bureau chief for the Arabic channel, revealed in an interview with Time in February that it was "hundreds of millions of dollars annually". Indeed, it is difficult to imagine how the network would survive, let alone thrive, if the Qatari authorities were to turn against it. "Simply put, the Al Jazeera success story would not have been possible without Qatar's backing," wrote Cambridge's Hroub last month.

So far, Qatar and its emir have acted as a protective shield for both the Arabic and English channels. Al Jazeera has come under "immense pressure" from regional governments, says An­stey; the network has, at one time or another, been kicked out of virtually every country in the Middle East. But, claims Anstey, he has never been subjected to any pressure from Qatar itself. It is a view echoed by Souag, Khanfar, Hannah and every other Al Jazeera journalist I speak to in Doha - on and off the record. For example, Jon Blair, the Oscar-winning documentary director, who joined Al Jazeera English at the start of the year, says: "There is a total absence of interference from above."

Self-censorship, however, is a different matter. "I think you would be hard-pushed to do a film on homosexuality in the Middle East," says one senior Al Jazeera executive. "It flies in the face of Wahhabi Islam. And so there is an element of self-censorship." But, he adds defensively, "The same thing goes on at the BBC."

The channel's foreign critics, especially in the US, don't agree. Cliff Kincaid of Accuracy in Media, an American conservative media watchdog group, refers to Al Jazeera as a "government-funded propaganda channel". In a blog post on 6 March 2010, Kincaid quoted from an Amnesty International report calling for "urgent action" on the arrest and detention of a Qatari human-rights activist, Sultan al-Khalaifi. Yet the story on the website of Al Jazeera English ended with the line, "The Qatari government could not be contacted for comment." "How is it possible that a channel based in Qatar and funded by the regime could not obtain a comment from those who pay its bills and pick its personnel?" he asked in his post.

Al Jazeera's coverage - or lack thereof - of the protests in Bahrain has also come under heavy criticism in recent months. Perhaps, say the critics, it is because of the historically close relationship between the royal families of Qatar and Bahrain; the two tiny nations belong to the Gulf Co-operation Council (GCC).

Anstey rejects the charge of bias and says the English channel has done "50-plus" stories on Bahrain. He cites the documentary Shouting in the Dark, produced by Al Jazeera English and aired on the channel in May. Filmed by an undercover crew, it meticulously documents the ruthless and violent suppression of pro-democracy protesters by Bahraini - and Saudi - security forces.

It is important here to distinguish between the English and Arab channels. When western politicians or journalists speak of Al Jazeera - especially when they do so in negative or critical terms - to which are they referring?

The award-winning (and bilingual) Palestinian journalist Daoud Kuttab is a close watcher of both. He finds a distinction between the louder, more "hostile" feel of the Arabic news bulletins, and the quieter, mellower, more ­considered tone of the English channel. "[Al Jazeera Arabic] keeps you on the edge," Kuttab told the American Journalism Review in April. "Its reporters are pushing issues rather than just reporting on them. They become more like activists at times, very in your face. The English channel uses more neutral terminology."

Coverage of Bahrain is a classic example of the divide. "It's true that the Arabic channel hasn't done enough on Bahrain," says a senior producer on the English channel.

Ghassan Ben Jeddo, a Beirut bureau chief for the Arabic channel, quit in April in protest at its neglect of the state-sponsored violence in Bahrain. Meanwhile, Sheikh Yusuf al-Qara­dawi, an Egyptian Sunni cleric who lives in Qatar, and whose show, Sharia and Life, is broadcast by Al Jazeera Arabic, claimed on air that "there is no people's revolution in Bahrain but a sectarian one" - implying that it was an attempted Shia takeover of the Gulf kingdom, somehow distinct from the wider Arab spring.

I point this out to Souag, who shakes his head. "The coverage is completely even," he says with a dismissive wave of his hand. He says the Arabic channel had to weigh up each country and each protest movement and, in Bahrain, "we did so in spite of the fact our office was closed and our correspondent was not allowed to work [by the Bahrainis]. We were allowed to send one person there for a very short time and then he was then thrown out. So we didn't have the resources to cover it in the same way but we did try to do it." He becomes animated: "When people ask us why we have not been covering Bahrain, I ask: 'Have you been watching Al Jazeera or living on another planet?'"

Khanfar, however, is much more blunt when I ask him whether Al Jazeera gave equal coverage to Bahrain. "Not equal, no," he says. "Each revolution, each uprising, had its own weight based on its strategic importance, based on its impact across the region. You cannot compare the revolution in Egypt with the uprising in Bahrain." Khanfar is also adamant that the Sunni/Shia divide had "nothing to do with it": "If it was [about] Sunni and Shia, why did we cover the war in south Lebanon, which was all about Hezbollah, a Shia party? Why did we cover all the stories in Iraq, without differentiating between Sunni and Shia?"

Then there is the US, which, despite being an important strategic ally of Qatar, has had a rocky relationship with Al Jazeera. The network provoked outrage in the States by airing video messages from Osama Bin Laden in the wake of 9/11 and by highlighting atrocities carried out by the US military in Afghanistan and Iraq. In 2005, it was alleged that George W Bush had discussed bombing the Al Jazeera headquarters in a meeting with Tony Blair; the British premier is said to have persuaded the US president that it was, to put it mildly, a bad idea.

The US did, however, bomb the Al Jazeera bureaux in Kabul (in November 2001) and Baghdad (in April 2003). The latter attack took place despite the network having provided the Pentagon with the street name and map co-ordinates of the office, and resulted in the death of Tareq Ayoub, a reporter. (Outside the newsroom of the Arabic channel is the Al Jazeera "museum" - a rather macabre, dimly lit, high-ceilinged room. Within is the vest worn by ­Ayoub on the day he died, along with his press pass, a handwritten draft of his final report and bits of rubble from the Baghdad bureau.)

These days, relations between the US and Al Jazeera are beginning to thaw, with the US Secretary of State, Hillary Clinton, extolling it in March as "really effective" and "real news". The startling conversion of Donald Rumsfeld perhaps best sums up the extent of the transformation of its image in the west and, in particular, in the US. "I can definitively say that what Al Jazeera is doing [in Iraq] is vicious, inaccurate and inexcusable," the then US defence secretary remarked in 2005. Yet, in a candid interview with David Frost on his Al Jazeera English show in September this year, Rumsfeld heaped praise on the channel, declaring that he was “delighted you are doing what you are doing".

In Doha, Anstey beams with pride when I mention these comments. "We were very pleased to be recognised," he says. "The next stage of our evolution is to be seen by more people, to push out and build our reputation. Get out into the American operators."

Al Jazeera's campaign to get access to the major US cable providers - from which it has been all but banned since September 2001 - was boosted by the fact that US viewership of Al Jazeera English's live web stream mushroomed during the Egyptian uprising - its website now receives more than 22 million visitors a month.

But one source at the channel tells me that Al Jazeera's desire to be "taken seriously" - as a February 2006 US state department cable released by WikiLeaks put it - might undermine its independence and integrity. And some of the more conspiratorially minded observers of the network have claimed that Khanfar was ­removed for being too close to the Americans; they point to a WikiLeaks cable that suggests he may have bowed, in 2005, to US diplomatic pressure and toned down the Al Jazeera website's coverage of civilian casualties in Iraq.

Intriguingly, others say that Khanfar may not have been pro-American enough for the Americans - or the Qataris! “The WikiLeaks stuff is a red herring," says a senior source at the English channel. "There was always a concern among the Qatari royals that Wadah was a bit too much of a voice-of-the-people, too pro-revolution, too progressive."

The new director general, Sheikh Ahmed bin Jassim al-Thani, is, by all accounts (he turned down my request for an interview), bright, ultra-competent and, by Gulf Arab standards, progressive. And one reason he may have been chosen to replace Khanfar - "a hack, not an administrator", in the words of one executive - is to provide some order and stability to the ever-expanding but deeply turbulent media empire. Employees at the English channel, in particular, have long complained about the management style and structure. It is still a "bureaucratic nightmare" says one senior producer, while another tells me that "morale and goodwill is being eroded by bureaucracy, poor management and a lack of clear leadership".

Anstey admits that there were "challenges from pre-launch to the first couple of years on air where we were evolving extremely fast" and where the "basic challenge was of starting up a channel of this size, with staff from 40 different nations, different backgrounds and networks, and assimilating them into one company, one vision". But, he adds, "it has hugely settled in the past two or three years".

Shortly after taking over, the new director general is said to have called together his most senior managers and executives for a meeting. "What do you think about breathing?" he asked them. They looked, understandably, perplexed. He continued: "And what do you think about your heart beating?" Another pause. Silence from the staff. "What I want," the sheikh told them, "is for employees of this organisation to think as little about administration as they do about their breathing and their heartbeats."

Nonetheless, does it make sense to have one of the world's most successful and influential media operations led by a technocrat, not a journalist? One ex-employee has his worries. "The message is clearly that the state will be exerting more direct control over one of its most prized assets," wrote Will Stebbins, the former Washington DC bureau chief of Al Jazeera English, in the Columbia Journalism Review.

The DG's surname is not the issue, counters Khanfar: "the issue is to what extent he will be guaranteeing editorial policy". For the former director general, Al Jazeera's 15-year record, its independent-minded and experienced editorial staff across the world and its army of loyal but informed viewers will continue to ensure the independent spirit of the network. "Our" - Khanfar still uses the possessive - "viewers are so clever and politicised that they'll be able to sense any change. And once people realise you have become a tool for a political party or government, they will drop you. Whatever you achieved in years can be dropped in a few days."

Meanwhile, Al Jazeera's historic achievements could be under threat from another, more unexpected, direction. Writing in the journal Foreign Affairs in September, Seib wrote of how "the revolutions that the network helped drive have unleashed a cascade of largely local news outlets, which provide more direct competition" to Al Jazeera. The network will be "to a certain extent, a victim of its impressive success and is unlikely to retain the dominance it once enjoyed".

It would be a mistake to underestimate Al Jazeera and, in particular, its durability. Its energy and dynamism this year have left its western rivals looking slow-footed and lacklustre. The Doha-based broadcaster will continue to be a thorn in the side of tottering dictators and despots across the Middle East.

Mehdi Hasan is the NS's senior editor (politics)