Wanted: new partner for 3,000-mile Amazon trek - must have own iPodRow over MP3 player is final straw for adventurers facing piranhas, peaks and MaoistsEsther Addley The Guardian, Thursday July 10 2008 Article history The pair were equipped to cope with Amazonian perils such as piranhas. Photograph: Ricardo Beliel/Alamy

It was to be the expedition of a lifetime, two friends and adventurers who set out to complete the first source-to-mouth walk of the Amazon, a 4,000-mile trek which they expected would take 18 months.

But while Ed Stafford and Luke Collyer had foreseen everything from piranhas to Andean peaks and Maoist revolutionaries, they could not prepare for something a little more prosaic - falling out over an MP3 player.

Today Collyer, 37, an outdoor activities instructor originally from Sussex, is in Lima awaiting a flight back to the UK while Stafford, a 32-year-old former army captain from Leicester, is hacking his way through dense Peruvian jungle alone, after the pair had a bust-up having completed only an eighth of their journey.

Stafford is advertising for a new companion - one with whom he can get along. As a press release issued yesterday put it: "Must have GSOH, no fear of snakes or gun-toting guerrillas, have three months to spare, an interest in the environment and an ability to walk long distances without asking 'are we nearly there yet?'"

Ed Stafford (left) and Luke Collyer found the ultimate test was each other The pair, both experienced adventurers, have known each other since 2004 when they met while leading separate expeditions to Belize and got on "like a house on fire". They decided to embark on the record-breaking walk, Stafford recently wrote on the expedition blog, "over a drink".

The intention was to raise awareness of climate change and raise funds for a number of medical and conservation charities. "We came to the decision that walking the river would provide us with the ultimate challenge that we were looking for. The fact that no one had ever done it before was hugely exciting and has spurred us on to get to the mouth."

Almost 90 days in, the strain was showing. Early last week Stafford wrote: "If I'm honest at this stage the hardest thing has been getting on well with Luke ... Basically when your brain has nothing to focus on it can direct this energy into the only thing it can - your partner! We knew that we could be susceptible to this but underestimated the degree."

"I have to agree with Ed on this," Collyer wrote. "So far we have had to deal with dry arid desert conditions, altitude, snow and freezing temperatures, steep climbs followed by steep descents, and fast flowing rivers. But the real test has definitely been with each other."

Exactly what the problem was remains unclear, though according to the expedition's PR representative, Vikki Rimmer: "They admit they weren't good at expressing their feelings." The final straw came last Thursday when Stafford admits he got into "a bit of a mardy" over a supply parcel that Collyer had ordered from the UK which he feared would be too heavy.

"I insisted that Luke wrote an email to ... his fiancee's mother, asking her to only send specific items essential to the expedition. I could tell he was not happy but I wanted to make sure we were not sending stuff unnecessarily. On the list Luke read to me was 1 x MP3 player. This annoyed me, as he had told me he was ordering one and offered to get me one too.

"I said to him, 'Mate, why have you only put 1 x MP3 player? You know that I wanted one too.'

"'Because I'm leaving the expedition, that one's for you,' said Luke."

Neither man was available for comment yesterday - Stafford's satellite phone, according to Rimmer, was off, while she had no contact for Collyer in Lima.

Stafford is currently in an area of Peruvian jungle controlled by the Maoist Shining Path guerilla group, she said, which along with the dense jungle canopy meant he might be unable to power up his internet connection to check his email or update his blog. She was keen to stress that the split had been as amicable as possible, releasing comments from the two men wishing each other well.

"I didn't want to end up bitter and angry with [Ed] after two years, and our friendship meant a lot to me," Collyer said.

"I'd like to say thanks for everything mate and good luck in whatever you decided to do now," his former partner responded.

The website might suggest otherwise, however. Collyer's photograph, and any mention of him, have been removed from the home page, which now reads: "On April 2nd 2008, Ed Stafford started his attempt to walk over 4,000 miles from the source of the Amazon river in southern Peru to the mouth in Brazil. The expedition will be uninterrupted ..."

Rimmer said this omission was because Collyer had yet to confirm how he would like to be represented on the site, and insisted there was no ill-feeling between the two men.

The new companion, she said, would be selected by a panel put together in the UK, comprising a survival expert - who would know the levels of experience and fitness required - a close friend of Stafford who could advise whether they would get on, and his mum.

The type of person sought? "I think that it would need to be someone who wouldn't hold Ed up or cause him any problems."

Might that mean someone who would defer to his leadership a little more than Stafford had done? "That might be fair," Rimmer said.