Ewan & Charley's awfully big adventure

It's not hard to see the appeal of Charley Boorman and Ewan McGregor for TV viewers. They're the male-buddy pair from Easy Rider, only without the drugs. They're intrepid English travellers, in the tradition of Robert Byron, Bruce Chatwin and Michael Palin, only with more swearing. They're rough-and-ready, sleep-under-the-stars, oil-on-my-denim-jacket roustabouts who happen also to be well-off actors, taking a break from the graft and the glamour of the big screen. They are epitomes of laddishness who would never be found reading Nuts or Zoo. For all the dust in their hair and gunge under their nails, they're nice boys, plucky descendants of those Victorian explorers who tracked the source of the Limpopo, heedless of the headhunters, cannibals and curare-tipped spears that they would almost certainly encounter en route. Their sweaty grins and capacity to endure rough camping conditions have endeared them to the British public as surely as if Jamie Oliver and Nick Hornby had formed an inexplicable alliance and ridden across the Sahara by tandem.

McGregor is most famous, globally speaking, for playing the young Obi-Wan Kenobi in the later (ie the earlier, prequelly) Star Wars movies, a career move he later publicly regretted (all that bogus sabre-wielding); but his reputation was made long before, when he played Renton, the charismatic junkie in Trainspotting. He matured into a dashingly convincing romantic lead in Moulin Rouge, A Life Less Ordinary and Young Adam along with several, more forgettable, star vehicles. He's listed at No 36 in Empire magazine's Top 100 Film Stars of All Time. Charley Boorman is less renowned than his friend, but has starred in umpteen movies, many directed by his father John: Deliverance (he played Jon Voight's small son), Excalibur, The Emerald Forest, Hope and Glory.

The two men met in 1997 in Cork on the set of The Serpent's Kiss, a 17th-century costume drama about topiary, leeches and treachery, and the two hit it off over talk of throttles and exhaust pipes. They share a love of bikes that borders on the obsessive, and a fondness for each other that's heartening to watch.

In 2004, they hit the road together on BMW Adventure bikes, journeying from London to New York via central and eastern Europe, taking in Russia, Kazakhstan, Mongolia and Canada, and visiting places where the charity Unicef has a presence. Having taken the precaution of bringing along a cameraman called Claudio von Planta, and some back-up vans containing a film crew and lots of equipment, they turned it into a six-part TV series called Long Way Round. A book of their exploits followed and was a huge bestseller. It's no great surprise, then, to find them repeating the exercise in Long Way Down, which records the 15,000-mile trek they made this summer, from May to August, from John O'Groats in Scotland, through Italy, thence to the Sicily ferry to Tunis on the northern tip of Africa; then journeying down the whole continent to South Africa, taking in 18 countries on the way.

It's the same mixture as before of travelogue, male bonding and social conscience, but with a slightly edgier feel. From the start, as they set up an Operations HQ in London, things go spectacularly wrong. The American producer-directors aren't granted travel visas by the Libyan embassy (peevish memories of all that bombing in the 1980s, I expect). A training course, to accustom the boys to "hostile environments" in Africa proves so gruelling, you can see their enthusiasm leaking away. Ewan breaks his leg coming off his bike at the traffic lights in Holland Park. Then Charley's wife is diagnosed with pneumonia and a collapsed lung. When the trip proceeds (with Mrs Boorman's blessing), they fly to Scotland to begin the trip. But Charley gets into a row with an airline official. When she asks him to move his rucksack, he replies, "Why? There isn't a bomb in it," and is instantly arrested and banned from all airlines in the world ...

The succession of misfortunes makes, it must be said, for good TV in a series which might otherwise drown in manly hugs, family sentiment and cries of rapture at the beauty of the landscape. One problematic strand concerns McGregor's wife Eve Mavrakis, a French production designer, who decides, early on, she'd like to accompany the boys, despite never having ridden a motorbike before. Students of psychology, and the "leakage" of inner thoughts, will enjoy Charley Boorman's troubled face, as he digests the information that his laddish voyage alongside his best buddy is to be invaded by (urgh) a soppy girl. A girl, moreover, who couldn't tell a Kawasaki from a KitKat ...

I meet the boys at BBC TV Centre in west London. Since Ewan's 36 and Charley 40, it's absurd to call them "boys", but that's exactly how they come across, as they welcome you into a glass-walled room and offer you coffee, fruit and cheese. Ewan is, like all actors, shorter than you'd expect, but is bright-eyed, scarily alert, and possesses the confidence of the devil. His voice slices through the room like a machete. He does most of the talking. Charley, by contrast, is rumpled and endearingly uncoordinated, and his eyes widen like saucers when he wrestles with memories or difficult concepts. He grew up in Ireland, riding motocross bikes from an early age. He took part in the Paris-Dakar rally last year, and is, bikers will tell you, held in high esteem by the leather-gauntlet fraternity.

I ask about on-bike music. What's the best thing to have on an iPod when you're doing 100mph in the Mont Blanc tunnel? "I never break the speed limit," deadpans Boorman, "so I wouldn't know." "Snow Patrol," says McGregor, "and an American band called Bonnie Prince Billie. I was introduced to them by the actress Michelle Williams." Was that it? Not "Born to be Wild"? Not Chris Spedding's "Motorbikin'"? "I listen to a lot of KT Tunstall, and the Stereophonics," says Boorman. Whaaat? "And the Black Rebel Motorcycle Club." That's more like it.

How many plans were rejected before they came up with Long Way Down? Had there been a Long Way Up and a Long Way Across? "About the time Long Way Round went on the air," says Ewan, "we looked at the world map in our office and saw two possibilities – down through Africa, or up through the Americas. Though Charley's been talking about a diagonal trip through Asia to Australia."

Long Way Diagonal – that didn't sound right. "Getting there through India and the Stans would be amazing," says Charley. The Stans? "Kazakhstan, Uzbekistan – those Stans."

The big question is: why bikes? The pages of the tie-in book are often damp with misery, as Ewan and Charley become saturated with rain and physically silted-up with sand (which gets everywhere) after travelling exposed to the elements. Did it have to be a bike ride? This draws a lengthy rhapsody from Ewan: "Riding motorcycles was a dream I had when I was a kid. I was never allowed a bike when I was a teenager, so it really was a dream for me, and I never quite got over it. I just love them as objects; I like looking at them and cleaning them and tinkering with them, even if I don't know what I'm doing. Riding them isn't like anything I know, it fulfils a big part of my life. I love the idea of getting from one place to another on them – but long distances thrill me more than going to the shops."

"It's a choice you make," says Charley. "People choose to ride a bike because they want to. It's not an economic necessity. The thing about a bike is, there's no phone, there's no passenger seat and no papers to put on a seat, to start reading in traffic jams. You have to concentrate because it's easy to get knocked off. And by the time you get home, your mind is clear."

They'd been influenced in their quests by books and films. "My favourite traveller? Easy," says McGregor. "Ted Simon and his book, Jupiter's Travels. He was a Sunday Times journalist, and decided he wanted to travel the world in 1972 and do it by motorbike. So he bought a stock Triumph, and went round the world ... It took him four years. It's a brilliant travel book. We got in touch with him at the end of Long Way Round, and he came out and joined us in Mongolia. Without that book, we might not have come up with the idea of doing the first trip." A look of pure hero-worship comes into his eyes. "One of my favourite movies," says Charley dreamily, "has to be On Any Sunday, the documentary, directed by Bruce Brown. It just makes you fall in love with riding motorbikes."

They took with them lightweight tents, in which they slept between sojourns in cheap hotels. Did the joy of camping wear off after a while? "No it didn't," they say in all-but-chorus. "The nasty hotels were the worst sight," says Charley with feeling. "You'd find yourself sleeping on your rollmat and your sleeping bag on the bed because you think, I am not sleeping in that. No part of my body is going to touch that sheet. And you'd have been much better off putting your tent up."

Had they been universally welcomed during their 81-day burn through the Dark Continent? "People still have a biker image in their heads that hasn't changed from the 1950s," says McGregor with a touch of bitterness. "Sometimes you can't get a table in a restaurant. Sometimes hotels become mysteriously full. But mostly we found people were willing to help you – maybe there's some subconscious realisation that you've been battered by the elements, that if it's a fucking hot day then you're fucking hot and if it's a wet day then you're wet, and they tend to look after you because they know you're vulnerable."

Yes, but did they run into trouble – violence, threats, bribery, theft? "So many people, when they knew we were going, told us about Africa," says Charley. "How the hyenas would eat your face, how you'd walk out of a bar and someone will machete you to death. People have this idea of Africa as a dodgy, dangerous place. And you ask, 'Have you been there?' and they go, 'Well, no I haven't actually been.' Now, we've been to Africa before, and in the towns you'll find kids who'll try and lift your wallet, but you get that in London. And 99 per cent of the time, where we went on bikes, people were friendly, interested in where we'd come from and what we were doing. They always laughed when we said we'd come from Scotland and were going to Cape Town, like, what d'you wanna do that for?"

They did, on the other hand, see a lot of guns. "But they were more for show than anything else. In Ethiopia we saw some spectacular desert warriors, with marvellous 1980s hairstyles all crimped, like Prince's, and with their tribal dress they wore these shiny, polished-up AK-47 rifles. But they were just a status symbol or a decoration. You couldn't imagine they had ammunition in them."

"Bloody expensive, ammunition," says Charley, with the air of a man who knows.

Things had become a bit lairy in Kenya, where they were given police protection – not from muggers, but from a sinister gang of Somali bandits called the Shifter. "They offered us soldiers to escort us in case we walked into something, but nothing happened," says Charley. "We were lucky. If you're unlucky ... we came across a school where there had been this terrible massacre, a year and a half before: some soldiers had come in and murdered 22 children and 52 grown-ups in the village. It was awful." Otherwise, the only danger on the trip had come from wildlife. Ewan found himself in trouble for dissing an elephant. "It was in the Okavango Delta [in Botswana]. There were two elephants near our rooms, and I got a bit cocky. I began filming myself, with an elephant in shot over my shoulder. As I walked away one started following me, doing that false charge, with its ears up, trumpeting. I probably wasn't in real danger but I felt real fear. I said, 'Come on Ewan, you don't know what you're doing. It's an elephant. You're not in Scotland. Show it a bit of respect.' If it had decided to come for me, there's nothing I could've done. When people get trampled by elephants, you don't suffer a broken leg, you die."

After all the laddishness, the boys-together, lighting-your-farts hilarity, Boorman and McGregor received a reality check when they visited Unicef sites as part of their charity mandate. "We visited three of them, one on the Eritrean-Ethiopian border, where we met kids who'd lost their limbs to landmines. Then in Gulu, northern Uganda, we visited a couple of kids, a guy and a girl who'd been abducted into the Lord's Resistance Army and lived a life of absolute fucking terror and horror. They were taken away at seven into this rebel army; she'd been raped, used as a whore by the army general, made to maim, to kill and torture. The way the army keeps these kids is to take them back to their villages and make them kill people there, even their own families. They're made to kill their own friends, even their brothers and sisters, so that they're completely cut off. The girl came back to her village at 15, pregnant, and now she's got a two-year-old kid. She probably has no chance of getting married or employed. Her life's been ruined." Did she talk about experiences? "No," says Charley. "Her community around her were scared of her. You cannot believe what these kids have gone through. Unicef work hard trying to rehabilitate them back into society, if they're lucky enough to come back. Thousands of children are abducted, but only hundreds come back."

The boys refuse to answer provocative questions about the highs and lows of their relationship, as they lived in each other's pockets for three months. What did each consider to be the other's worst habits? "That's a horrible question to ask," says Ewan. "Charley here is perfect in every respect, whereas I'm a bit of a nightmare." (Charley doesn't play ball either, but carefully blames any moments of friction between them on a chronic lack of food.) Nor do you get far by asking about Ewan's wife Eve, who eventually came along just for a short burn through Malawi and Zambia. Had she come for the whole trip, would Charley have pulled out? He sidesteps the question: "She came along to Malawi and had an amazing time, and was a tremendous asset to the whole enterprise. And," he continues, going perhaps further than he meant, "she showed that anybody can go on this trip. It doesn't matter who you are, you can go and do it." Even girls, eh?

The boys are staying home for at least three years before they'll try another trip. There are movies to be made, and families to re-connect with, and signing tours of the new bestseller. As for the lessons learnt on the trip, McGregor has entered a realm that's pure Buddhism. "You know what I missed? I didn't miss anything at all. In fact, if I could've taken less, I'd have been happier. There's something very pure about having nothing at all, about leaving your house with nothing in your pocket, no phone, nothing. I love that. On a trip, of course, you have to take stuff. But the nirvana state would be to have nothing at all."

'Long Way Down' starts tomorrow, 9pm on BBC2