Army captain Louis Rudd said last night he was “absolutely elated” to have completed a solo, unsupported crossing of Antarctica, revealing he had relied on supplies of Dairy Milk bars, Asda’s tropical mix and three biographies of Winston Churchill to see him through.

Rudd, who became the first Briton and second person to finish the 925-mile expedition late on Friday, completed the gruelling crossing within two days of American athlete Colin O’Brady. The men had spent two months locked in an epic race which had echoes of past polar feats, including the British and Norwegian push to the south pole over a century ago.

“I’m absolutely elated, and relieved that I’ve managed to complete the journey,” Rudd told the Observer in a satellite phone call from his tent, which last night was pitched above the frozen Antarctic coastline. “It’s a minor miracle that both of us actually completed this; the odds of both of us doing it were so slim.”

A major inspiration for the 56-day expedition was the loss of his friend, Henry Worsley, a fellow explorer who died while attempting to break the same record nearly three years ago. Rudd carried a flag with Worsley’s family crest on the journey, even though he stripped all other provisions down to such bare essentials that he didn’t carry a change of underwear. “The fact that Henry’s flag made it all the way across, that means a great deal,” he said. He hopes to speak to Worsley’s widow today.

Both Rudd and O’Brady travelled across Antarctica on skis, pulling all their provisions behind them on special sleighs for more than 50 days. They were forced to weigh up the need to consume up to 10,000 calories a day against the challenge of pulling anything they wanted to eat along with all their other supplies.

But while O’Brady is a professional athlete who travelled with protein-packet “Colin bars” tailored to his needs by nutrition specialists, Rudd took a more low-key approach to the “grazing bag” that kept him going through long days of skiing.

“My grazing bag is a tropical mix that I bought from Asda – I just grabbed what was available every time I went in, until I had 70 bags. Then there are Cadbury’s Dairy Milk bars, and some cheese and salami I bought in Chile [on the way to Antarctica],” Rudd said.

He had a freeze-dried meal in the evening, along with a protein shake, and porridge for breakfast with hot chocolate. Even so, he thinks he lost up to 15kg, nearly 20% of his bodyweight. “I’ve got chicken legs, my arms are stick thin,” he said. “I had to sew a tuck into the waistband of my underpants and thermal leggings after I felt them slipping down when I was skiing.”

Rudd admits he was blindsided by the transformation of his expedition into a global race. He only found out that O’Brady would be trying the same journey a few days before he flew out of Britain for Antarctica.

Facebook Twitter Pinterest Captain Louis Rudd. Photograph: René Koster Photography

He was glad media interest in an epic contest helped bring more attention to their expeditions and the causes Rudd is supporting, including fundraising for ABF The Soldiers’ Charity, but decided from the start not to treat the crossing as a contest.

“I didn’t want to get drawn into a race. I knew the expedition would be difficult enough as it was,” he said. “All that mattered to me was that I completed it, that I skied solo and unsupported, carrying the flag with Henry’s family crest.”

There were times when he found it hard to push on. “I skied through some horrendous conditions,” he said. “I would be skiing along thinking, ‘my God, this is the worst place in the world right now; this is horrific’.”

Rudd is one of the most experienced polar explorers in the world, but the trip went far beyond anything he had attempted before, not only in terms of its length but also the solitude. It was his first solo expedition, and it would last around two months.

“In normal life, in military service you don’t end up in those situations, I’d probably never spent more than a couple of days on my own prior to this expedition, if that.”

A small collection of audiobooks, including military history and four biographies of Churchill – he got through three – provided something like company, and sometimes he skied to music, including U2 and Pink Floyd.

There was one rare, and moving sighting of a bird around 20 days into the trip. “I’ve never seen any kind of wildlife (in Antarctica) before,” he said. “I was skiing in some really difficult conditions, I looked up and saw a white snow petrel flying about 10 feet in front to me,” he said. “It was just looking at me, checking me out. That was just a really unusual encounter.”

Beyond that the only other life he saw was a brief stop at a scientific base at the South Pole, where around 15 to 20 people were waiting to cheer Rudd on. He could talk to them, but not go inside, or even accept so much as a cup of tea without his trip losing its “unsupported” status.

“I stayed for about an hour and as I skied off it was quite daunting to suddenly be on my own again,” he said. “I didn’t stay too long deliberately, as I was keen to get away from temptation.” Rudd is now relaxing with O’Brady in temperatures of -10 degrees – which after the extremes of his trek “feels almost tropical” – and enjoying supplies buried a year ago for another explorer who attempted but didn’t finish the trip.

“We are camped 10 feet apart,” he said. “There’s some coffee and milk powder so we are sat feasting like kings on things buried in the ice for a year, but it still tastes good.”