Pop stars, eh? Sometimes you wonder whether they can walk and chew gum at the same time. Well, don't worry about Jarvis Cocker: the man can walk. Six miles. And eat energy bars. And only whinge a little bit. (Well, he was tired.)

This is madness. It's 10.28 on an unfeasibly sunny April morning and I'm standing with a photographer outside Euston's Paperchase waiting for Jarvis Cocker to join us for a lengthy ramble. He's late, but I never believed he was coming anyway. Jarvis is a household name. Like he's gonna spend the day trudging through fields with two strangers.

But there he is! Hurrying towards me in a green parka. Somehow I'm surprised he hasn't made any effort not to look like Jarvis Cocker. 'Nice day for it,' I say as we dash for the train. "Yeah," says Jarvis, flatly. He answers his phone, and we climb aboard.

Why are we doing this? Well, last year Pulp released an album - a very good album - called 'We Love Life' that showcased the band's fondness for nature. Jarvis talked about wildlife in interviews. If he likes it so much, we said to his PR, let's do a country walk with him. That was last June. Finally - after many phone calls - they agreed. Jarvis picked a 10.8-mile walk from the 'Time Out Book of Country Walks'. We said he must do it all and that, no, he couldn't cycle or do a mile then get a taxi. Which probably explains why he's looking grumpy. And why he's telling the caller he's gonna ask to be let off cos of a bad back.

After the phonecall, conversation isn't easy. Jarvis got back from DJing in Iceland yesterday and looks tired. A ten-mile walk clearly isn't a priority. "I find walking boring," he says. Oh. They never told us that. "I'd rather write a song about nature than visit it." Suddenly I realise how my dad must've felt, dragging me on day trips I didn't want to go on. "I just don't feel very well," he says. Then, with the slightest smile, "But at least it's not raining."

After a brief, stilted chat, Jarvis pulls a laptop from his satchel (ah, the essential walking accessory!) and types his Icelandic diary for a magazine. At Bletchley, we sit on the sunny platform, awaiting our connection to Bow Brickhill. Jarvis has cheered up. He likes being outdoors - "especially now the weather's getting better". He doesn't like rain, though. Good job today's weather's so fantastic."Well, I'm good like that," he says. "I've already pre-arranged that the days when we do the forest concerts will be the same."

The Forestry Commission came to Pulp with the idea for the five shows in woodland clearings. "I wonder about the creatures that live in the forest," says Jarvis. "I imagine loads of badgers and foxes going, 'Fuck off! I can't stand this row!'" It's nice for the band to do something new, though. "Yeah, the idea of it becoming routine and commonplace is crap. It's like sex becoming routine and commonplace. You have to get suspenders on, metaphorically speaking."

Jarvis's phone rings again, but he misses the call. "You're gonna think I'm a mobile phone junky." He's on pay-as-you-go and low on credit, so I offer mine. "Can I? I've only got 68 pence and that won't get me far." He tells his pal Iceland's Blue Lagoon may be responsible for his dodgy guts.

It's midday, and we clamber on the train for the two stops to Bow Brickhill, where our walk begins. Jarvis, in a thick parka, blazer and shirt, isn't exactly suitably attired, but after we turn off a quiet country lane on to a footpath he seems happy enough. "Now we're here, it's quite nice," he admits. We feed some horses, Jarvis swings awkwardly on a rope swing, and then we reach a field of sheep. "You're not gonna bite me, are you?" he says, as they trot over. "Actually, l've got a mate who thinks that, all their lives, sheep are looking for a way to die."

Jarvis, by now taking a leading role in reading directions, has heard many theories like that. He talks about a bear-infested wood he visited in the arctic circle. "Somebody told me if you see some bear shit, put your fingers in both ends," he says. "Whichever end is warm came out last, so he's heading that way. Problem was, when we got walking, we didn't know what bear shit looked like."

Apart from one wrong turn - where my pale companion seems slightly aggrieved - we're making good progress. Except Jarvis has decided he's getting flu: "I ache all over." He cheers up when he finds a conker with a shoot growing, proudly announcing he grew a tree at home from a twig. The sun's beating down, and the hilly terrain is wearing Jarvis out. I tell him people will be surprised he's really walking with us. "Even if we did it all," he puffs, "people would still say, 'I bet they just dropped him off with a helicopter at various points,' so we really may as well stop at half way." The pub at the five-mile mark looks a realistic target.

As we walk on, the directions say to ignore a left turning. "I'm not fuckin' talking to you," shouts Jarvis, as we pass. He seems chirpier. "It's nice to get out and about," he admits. Around 2pm we take a break at the side of a country lane to eat some snacks I'd brought. Having fun then, Mr Cocker? "It's all right," says Jarvis, munching an energy bar. "I'm not keen on the uphill bits. But this lorry is good." A lorry has rolled up, and the driver has climbed atop a crane on the back to load tree trunks on to his truck. "Bet he loves that job. It's like he's got a massive nob that can pick up logs."

Are you tired? "I ache a bit. But it's good. I find it slightly depressing that we've got about the same distance again before we reach the pub." Sorry. "It's all right," he chuckles. "Anyway, look, he wants to give us a lift..." A car is reversing up the road. We've had our first spotting. A lad jumps out and cries, 'Jarvis!' "Are you gonna give us a lift?" replies the pop star rambler. But, clearly in shock at having spotted Jarvis Cocker sitting by a remote road, he's already jumped back in and driven off. He'll never guess why you're here Jarvis. "Because I've got a new job monitoring log collection. He's doing a marvellous job."

He lies back, closes his eyes and takes another bite. "So is that what you're supposed to do on a walk? Have loads of sweet things?" Sugar gives you energy. "But don't savoury things give you energy? What about some Marmite sandwiches?" After three miles in a backpack? "I like it when they've had cling film on for a few hours. If you leave them all day they're like leather, but I like it."

After prompting, Jarvis admits Pulp are playing Reading 2002, at the request of The Strokes. Does he get involved in business-y decisions? "Very little. I'm rubbish. I ought to 'cos it's my livelihood, but I'm still holding on to the vestiges of my punk-rock attitude where that's not supposed to be the point. I'm the only one in our band who hasn't got a pension scheme. Just 'cos of that one word, "pension". It just sounds rare [Jarvis says that lots - it means very] bad. But I'll probably be fucked when I'm older and they'll be lording it up."

You must be financially secure. "Well, I lost a lot on Black Wednesday," he quips. "No. I'm not skint, but I dare say I've got less than people imagine. Quite a lot less." Must be annoying for musicians when people assume you're rich and you're not. "Yeah, but I used to assume that too. It's only when you experience it that you realise how penniless we are and how much sympathy and love we need. And if you see me in the street, just give me a fiver. Y'know, that'll do. Don't say anything. just put the fiver in my hand. I'll know what you mean. And that'll be beautiful."

Jarvis heaves himself up."We should get on, I'm meeting my best man later." He's getting married in July, to his fashion stylist girlfriend, in the Normandy countryside. Any more detail is blood/stone territory. As we ramble, Jarvis suggests other people Time Out could take on country walks. "Lenny Kravitz would be good," he says, dry as a camel's hoof. "I bet he's handy with a compass." His phone rings again. "It's really good," he tells them, "just a little bit far."

The sun is scorching, and Jarvis is tiring. "Glad I brought my laptop," he says, ruefully. But he's becoming increasingly playful. Another call comes as we amble towards a wood. "These motherfuckers are leading me into the woods again," he tells them. "They're gonna violate me. I can tell. It's like "Deliverance". Tell the police. You're my only hope." The next caller is told squirrels are affecting the signal. If I didn't know better, I'd say Mr. Cocker was enjoying himself. "I do feel our relationship has developed," he says.

Wandering through a field, he starts singing 'We Plough The Fields And Scatter', then stops to claim potato starch has leaked out and formed the white stones in the soil. He lies down in the field while we check directions. "Water," croaks Jarvis, who's necked the bottle I'd given him. "For God's sake, water!" Having decided the way, we reach a stile. "Get Paul Weller to come on your walk," says Jarvis. "You could call it Stile Council."

It's almost 4pm when we reach the pub in Woburn. Jarvis orders half a bitter shandy and goes to the beer garden. We've done five or six miles and he's visibly shattered. He takes one sip, puts his head on the table and nods off. Heading back to London is easier said than done. We can't find a taxi that'll take us to the station, so we try the bus stop. Amazingly, the first bus in three hours is imminent. But after his snooze, Jarvis is groggy and withdrawn. Which is why what happens next is so unfortunate.

The small bus arrives and we get on. 'Fuckin'hell, it's Jarvis Cocker!' We look round, horrified, to discover the only others on the bus are ten or 11 secondary school kids. But we all know this is our only way home. We sit at the front, and Jarvis ignores the shouted argument about whether it's him, and an impromptu chorus of 'Common People'. Throughout the day we'd barely seen anyone, and Jarvis had only been recognised by that lorry driver. But during the painful 15-minute bus ride I realise how hard it must be being Jarvis Cocker. We reach our stop and leap off just as they're coming forward for autographs.

On the London train, Jarvis takes off his specs, hugs his parka like a teddy and falls asleep. The day seems to have turned out better than expected for all of us - myself and the photographer are amazed at what a sport he's been. Not many international pop stars would spend five minutes with a journalist without a press officer nearby, let alone eight hours walking, talking and joking with them. I like Jarvis Cocker.

As we rumble back to London's stresses and strains, he awakes. Was it a worthwhile adventure? "Oh aye, yeah, definitely." He looks tired but happy. Last question, Jarvis - have you learnt anything today? "I'd say if you're gonna go on a walk, consider a stick. Could be useful. Takes your weight and if something attacks you you can hit it with it. And I'd say consider something savoury for lunch. Those things were good and I'm grateful you brought them, but maybe a pack of Bovril crisps. Or a Cornish pastie. Maybe even a flask. Quite a treat to have something hot. But yeah, it was nice. Thank you."