The London Irish full-back feared his World Cup dreams were over when he was banned from England's Six Nations title campaign for abusing an anti doping official.
Armitage then made things worse for himself when he was suspended again for punching Northampton fly-half Stephen Myler.
But the 27-year-old will complete a "massive turnaround" in his career when he lines up to face Argentina in Dunedin's futuristic new glass-roofed stadium.
And in doing so, Armitage will achieve an ambition he set for himself eight years ago, as he watched England win the 2003 World Cup.
"I didn't even think I'd be over here (in New Zealand as part of the squad)," Armitage said, when asked to reflect on sitting out the Six Nations.
"To have the opportunity to start now, I'm speechless, it's like a dream come true.
"It's everything I've ever wanted since I watched the final in 2003.
"I had just joined the London Irish academy and was in an academy house watching the final with Topsy Ojo, thinking 'one day, who knows, it could be us'.
"I'm over the moon."
Armitage will start on the left wing for the first time in a Test in place of Mark Cueto, who is still struggling with a back injury.
England manager Martin Johnson insisted Cueto is not a long-term concern but the Sale wing is short of full fitness and Armitage has been hammering on the door.
"Mark could have played this week, but it was a choice between a guy who's not quite where he needs to be and someone who is playing well and putting the pressure on us to pick him," said Johnson.
"The decision was a pretty simple one. Delon's raring to go. He's a very good footballer, he is in good form so you go with him.
"Mark is disappointed. He wanted to play but he'll be better for an extra week off and deep down he knows it's the right call for him as well as the team."
England's only other change from the Ireland victory is the return of number eight Nick Easter, who had missed the game with a tight calf, with James Haskell switching to the open-side.
Scrum-half Ben Youngs will make his comeback off the bench after a knee injury ruled him out of England's three warm-up internationals.
Armitage made his Test debut against the Pacific Islands in 2008 and enjoyed a flying start to his England career before injury and a chronic loss of form halted his progress.
Ben Foden took over as England's first-choice full-back at the end of the 2010 Six Nations and Armitage then undermined his own World Cup credentials by clashing twice with the authorities.
But England kept the faith.
"It's good on him for coming back," said Johnson.
"He had a couple of bans towards the end of the year but we brought him back into camp and said 'get yourself back to where you know you can be because you are a Test player'."
Armitage has responded positively, scoring a try off the bench against Ireland to force Johnson's hand into picking him rather than gambling on Cueto.
"I play a lot better with a smile on my face, when I am relaxed and enjoying it and recently I have got back to that," said Armitage.
"The style England are playing, the way we want to throw the ball around and the way we want to have a go, that suits the way we want to play."
Argentina named their team on Tuesday, making just one change from their warm-up defeat to Wales with former Harlequins and London Irish centre Gonzalo Tiesi returning to the midfield.
The Pumas boast one of the most ferocious forward packs in the game, so good is their front row depth that Leicester prop Marcus Ayerza could not make the 22.
Johnson insists there is more to Argentina's game than forward power, with Jonny Wilkinson's former Toulon team-mate Felipe Contepomi pulling the strings at fly-half.
Tiesi, Gonzalo Camacho and Horacio Agulla are all backs with Premiership experience.
"They do what they do very well but they've got more dimensions to them than is sometimes made out," said Johnson.
"They are a dangerous running side, they come at you through forwards but put you under pressure with their kicks as well.
"It's a full-on Test against a team that finished third in the world last time. You have to get it right in the moment, right from the opening kick-off."
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