The 27-year-old, who finished in ninth place during the 2014 run of BBC One’s business series, looked shocked when presenter Emma Willis announced he had won the Channel 5 show.
He hugged the man who had been his best friend in the house before exclaiming: “Omigod! Omigod!”
James Hill wins Celebrity Big Brother (Jon Enoch/Channel Five)
Likeable James had been favourite to win for the last few days, with odds as short as 8-15 with bookmaker Coral. He won many fans by keeping a steady head inside the fractious Big Brother house while so many others lost theirs.
During his interview with Emma, James seemed bemused to be crowned champion. "Wow! I can't believe it!" he repeatedly said. When asked why he thought he had won, he said: "I've been myself from the beginning. I just tried to stay grounded."
From Apprentice loser to Celebrity Big Brother winner(Channel 5)
However, his friendship with Austin was a constant theme: "I got close to some people in there that I hope I'll be close to for the rest of my life," he stated.
It was particularly apt that the final two in this UK vs USA-themed series were a Brit and an American. Runner-up Austin was magnanimous in defeat, telling James: "I love you, brother."
Austin came second (Jon Enoch/Channel Five/Press Association Images)
The 27-year-old left the house to cheers and gushed his adoration for the winner to a glamorous-looking Emma: "We've shared a bed together since day one," he said.
Viewers were captivated by the bromance between straight contestant James and gay housemate Austin; it proved a popular topic of discussion as the duo shared everything from cuddles to a bed.
Austin and James share a bed(Channel 5)
Talking about their friendship, the American said: “We're standing. We've been through this insane journey. I'm so glad that I've made a friend. That dude is a great guy, he's been a strong pillar and he deserves it.”
Natasha Hamilton (Channel 5)
Notably absent from proceedings was Teen Mom US star Farrah Abraham, following her altercation with former Big Brother housemate Aisleyne Horgan-Wallace on sister show Celebrity Big Brother's Bit On The Side.
The final produced one shock as Atomic Kitten’s Natasha Hamilton, previously the bookies' favourite to win, ended up in third place.
The 33-year-old told Emma, the Big Brother house was "like being in a pressure cooker that could explode at any moment".
Bobby Davro (Channel 5)
The pop star repeatedly butted heads with 24-year-old Farrah, but she decided not to be “a pushover” and stand her ground. “I'm not going to be bullied because I had all that when I was a kid, but I'm an adult now," she said.
Comedian Bobby Davro was greeted with chants of "Bobby! Bobby! Bobby!" as he took the walk down the steps in fourth position. "I would have liked to have made top three, but I’m not complaining," the funnyman said.
During his exit interview, Emma approached the subject of Farrah as the pair had frequently clashed: "She’s a particularly nasty person beneath that beautiful exterior. She's got to work on that."
Celebrity Big Brother’s Chloe-Jasmine, Sherrie, Emma Willis and Stevi (Channel 5)
However, an upbeat Bobby basked in the glow of his Big Brother experience: "There's no grudge against any of them, including Jenna Jameson and Farrah. They just had trouble adapting to our culture and sense of humour," the 57-year-old observed.
There were some boos when presenter Emma announced engaged X Factor couple Stevi Ritchie and Chloe-Jasmine Whichello (who count as one) in fifth spot. But Stevi said they hadn't expected to get to the final in the first place.
"We were so full of nerves and worried about our relationship the whole time," his fiancee added.
Celebrity Big Brother’s James Hill and Austin Armacost (Channel 5)
Responding to a suggestion that some didn't buy into their relationship, Chloe-Jasmine hit back: "We're not for sale, Emma." The 24-year-old blonde admitted: "Some aspects of our relationship we had to keep a lid on, which was incredibly difficult."
Loose Women's Sherrie Hewson ended up in sixth place. Dressed in a cream gown, she told Emma: "I've had the most fantastic time, but it's been an emotional rollercoaster."
Defending being voted as the 'most boring' housemate by the public, the 65-year-old said: "I'm normal and I'm not going to shout and scream and eff and blind for TV cameras."
Farrah Abraham and Jenna Jameson (Channel 5)
During the controversial series, glamour model Tila Tequila was removed from the house after only one day when it emerged she had made a series of anti-semitic remarks on social media.
The other stars who took part were: US actor Daniel Baldwin, The Bill actor Chris Ellison, presenter Gail Porter, US hip hop artist Fatman Scoop and US supermodel Janice Dickinson.
The UK vs USA edition is also memorable for an unusual twist – for the first time ever, a fake eviction was not quite what it seemed.
The public voted for Farrah and Jenna (collectively known as Jarrah) to be fake-evicted into a luxury suite to spy on the house, but the rest of the Big Brother housemates were in on the joke and made fools of them.
There was also the bizarre spectacle of Diana, Princess of Wales’s former butler Paul Burrell spending four days inside the house; he revealed that the only time the Queen carries money is for the collection box when she attends church.
However, the biggest talking point remains the Celebrity Big Brother Bit On The Side brawl. Police are investigating the row at Elstree Studios in Hertfordshire between Farrah and Aisleyne which saw ‘Allo ‘Allo actress Vicki Michelle caught in the crossfire.
The UK may have triumphed, but the US contingent can take some consolation from having provided more entertainment.
— Big Brother UK (@bbuk) September 24, 2015
The Americans, not just content to pick arguments with the home stars, frequently fought among themselves while the Brits made endless cups of tea.
After four weeks of tears and tantrums, it’s all over for another series.
Get the latest updates, reviews and unmissable series to watch and more!
Thank you for signing up to Whattowatch. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.