A British climber is in the closing stages of an attempt to set a world record for the highest mobile call.
Mr Baber has been in the Himalayas since mid-April
Rod Baber is making final preparations to scale Mount Everest and make the call from its north ridge.
Following weeks of acclimatisation, Mr Baber is now at base camp recuperating and checking equipment prior to beginning the actual ascent.
The expedition will begin its final push on 15 May and aims to reach the summit about eight days later.
Mr Baber reached base camp at the foot of Everest in mid-April and since then has been trekking up the mountain to get used to living at high altitude.
"It took us three days before we could walk more than 50 steps without running out of breath," he told the BBC News website from base camp in the Himalayas.
In the last few weeks the members of the expedition climbing Everest with Mr Baber have reached altitudes of 7,500 metres - the height at which most people start to need oxygen to continue.
"We've done some of the most physically demanding sections of the route," he said.
The trekking has meant that four members of the expedition have been forced to quit as altitude sickness has left them unable to cope.
Now the remaining members of the team, organised by the HimEx climbing group, is recuperating prior to the attempt on the summit. Mr Baber said he had already lost 11kg in weight and was likely to lose five more by the time the attempt was done.
Making a mobile call from the top of Everest has become possible as a base station installed in nearby China has line-of-sight to the north ridge of the mountain.
Phone reception in the Himalayas has improved as the Chinese army is also at the Everest base camp making preparations to take the Olympic torch to the summit.
Mr Baber said the expedition had a "very good" chance of reaching the summit if the weather stayed calm.
"But," he said, "it's when Everest lets you climb it, not the other way around."