Simon Ambrose has won The Apprentice, beating the show's favourite Kristina Grimes to the £100,000-a-year job with business mogul Sir Alan Sugar.
The public school-educated 27-year-old was chosen over the single mother, 36, who was visibly upset after the result.
Ambrose told BBC One's Breakfast he was shocked to win.
"Up to the 11th hour I thought Kristina was going to walk it. We have seen her deliver week after week. She's a fantastic leader."
He said he was keen to prove to Sir Alan that he was the right choice: "He's an entrepreneur, he has taken risks all his life. He is taking a risk with me and hopefully I will deliver."
He added he was looking forward to getting his teeth stuck into his new role, which will see him train as a chartered surveyor while working on a project to develop a hotel and golfing complex near Stansted Airport.
Kristina said she was surprised to have lost the contest.
"I felt I'd out-performed Simon - he's a lovely chap but I still think I should have won," she said.
'Bloody old fool'
Before announcing his choice for his third successful candidate, Sir Alan said it was "a very difficult decision".
"I've got someone who's very experienced. I've also got someone who's enthusiastic, a great talker and willing to learn," he said.
"But I'm thinking to myself 'do you want to be the headmaster again?'".
He told Simon that he "wasn't a good leader of people", but added that his "very good innovative ideas" had impressed him in the final task.
Sir Alan told him: "Bloody old fool that I am, I'm going to take that risk, you're hired."
Kristina, originally from Wicklow in Ireland, later admitted that she was devastated by the unexpected result, saying: "I came on this intent on getting the job with Sir Alan.
"My heart and soul was in this. I was so confident, I really was."
Kristina financed her own education after having a child at 17
Sir Alan said he would have offered Kristina "a job any day of the week" if the rules of the programme were different.
"I know in the past that I've tended to support the under-privileged - that may have been a coincidence. I always said that I don't care if you are born with a silver spoon in your mouth or have climbed up the greasy pole," he said.
The defeated finalist said to her opponent: "As I've said to you before, if you win and screw this up, you won't have Sir Alan coming after you, you will have me."
Simon, whose father is a multi-millionaire businessman, was ridiculed on the programme for being a bad landlord, after giving his tenants coathangers instead of a TV aerial when their television broke.
"Maybe I could invest in a few more coat-hangers, maybe even buy a TV aerial for some of them if they pay their rent on time," he joked after the final.
The pair's final showdown saw them compete to win over architects and property developers with a design for a building on London's South Bank, which Simon won.
Sir Alan later admitted that this year's final had been the toughest of all three series of the programme.