The man admired by presidents and warlords
Road blocks can be tricky things - not least for journalists. Grenades brandished at car windows on narrow roads. Bored kids with big guns looking to make a point.
Sometimes a piece of official paper will get you through. Or cigarettes. Or lots of smiles. But often - and without wanting to sound too melodramatic - the difference between safe passage and something much nastier can boil down to a word, a name.
Saying "BBC" has helped me plenty of times - certainly more times than it's hindered. I've shouted it out in Chechnya, Afghanistan and Somalia.
In 2011 we were waved down by sullen armed men on a country road in Ivory Coast. I could see four, maybe five people tied up in the bushes nearby, staring at us in silent desperation. "Are you French?" the commander asked, menacingly. "We don't like the French."
A few days later, further south, I had to beg for the life of our local fixer. He was Muslim. The soldiers made him kneel by a ditch, a barrel jabbing the back of his neck.
But saying "BBC" is only a small fraction of the story. If the name carries any magic on empty roads in troubled countries, it is only because of the journalists associated with it.
A few months ago, I was in Sierra Leone covering the Ebola outbreak and driving around with a man called Umaru Fofana. In Britain, you may have heard some of his reports on the BBC. But in Sierra Leone, his is an altogether different level of fame.
There is, I'm sure, no equivalent in Britain of Umaru. At any spot nationwide he is instantly recognised. Soldiers grin, demand a photo with him, then wave us past. Over decades, during Sierra Leone's civil war - when he was shot and jailed - Fofana has earned the respect that visiting journalists like me now shelter beneath.
There are plenty of Umarus across Africa, reporting for the BBC World Service. But there's also another name. A British one. It greeted me at the airport in Liberia just last month, as it has greeted me over the years in Abidjan, Kano, Mogadishu and Bamako.
"Are you Mark Doyle?" the taxi driver asked hopefully. "BBC? Ah Mr Doyle. Where is Mr Mark? Do you know him? Send him our greetings."
It happens every time.
Mark has been reporting on, and in Africa for the past 26 years. Not just parachuting in for the big stories but living here. Seized by an impulse to question, to understand, to get to the bottom of things.
Now, this week, he has left the BBC.
He's a tall, forceful but self-effacing character, who will probably find all this rather embarrassing. Too bad. For his is the sort of foreign reporting that matters, that endures.
Mark covered the genocide in Rwanda in 1994 - a deployment like no other.
"He stayed longer than any of us," his colleague Fergal Keane remembers. "Those who were in that awful place at that awful time will know what Mark Doyle gave for the cause of truth and for the BBC."
Canadian General Romeo Dallaire was in charge of the United Nations peacekeeping force trying to stop the genocide. He remembers a friendship forged under the constant threat of snipers, mortar, artillery.
"Courage, determination, street smart, astute and ethical beyond reproach. That was Mark Doyle," the general told me.
Sir David Richards has his own stories - he was in charge of British forces struggling to stop Sierra Leone's civil war in 2000.
He describes how Mark's, and Allan Little's reporting helped convince his bosses of the need for a more robust military intervention. "Hence the saving of thousands of Sierra Leonean lives that would otherwise have been at huge risk," he says.
Another of Mark's BBC colleagues at the time, Paul Danahar, describes how they made an experimental journey across the country to test the strength of the new ceasefire. Child soldiers waved them down at a rebel checkpoint outside Freetown. Guns were pointed.
And then Mark said, "Good morning," and the mood changed. They recognised the voice. In a country where children were being forced to murder each other, the man in the car represented a quality that had almost entirely vanished. Trust.
No wonder Mark himself tells of being ushered unexpectedly to meet African presidents who - having heard him so often on the radio - felt like they knew him as a friend.
I could go on. But you get the point. And lurking behind the nostalgia of this farewell speech, there is a broader point.
Africa is changing fast - booming in some places - with Twitter, mobile phones, a glut of information in more and more hands. But this is still a monstrously unequal continent and there is no substitute for the journalist who knows you don't find real news online behind a desk.
You find it down unnamed paths, beyond unpredictable roadblocks.
Twenty years ago, Rwanda descended into the madness of genocide. UN peacekeepers were stretched to breaking point - but one, Mbaye Diagne, stood out, taking huge risks to save hundreds of lives.
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