Walcott became England's youngest ever player at 17 years and 17 days in 2006 and was a shock inclusion in that summer's World Cup squad by Sven Goran Eriksson.
Then the Arsenal winger became the youngest player to score a hat-trick for England in the 4-0 win over Croatia in Zagreb in a World Cup qualifier in 2008.
But playing an active part in a major finals has eluded Walcott until now as he scored as a substitute and then set up the winner for Danny Welbeck in the 3-2 win over Sweden last night.
Walcott said: "To make my first tournament performance in a high-profile match means so much to me.
"It's been a long time coming and hopefully there will be more to come from me. It certainly whets your appetite.
"It seems only the other day, rather than six years ago, that I was picked to go to the World Cup as a 17-year-old.
"Now to finally play in a major finals is a special moment and one to saviour and remember, not only for me but for my family watching back home. I hope I can build on it."
England need only a point against the Ukraine on Tuesday in Donetsk to secure a quarter-final spot and Wayne Rooney will be available after suspension.
But Walcott feels all 23 members of the squad have to be up to speed and ready to play a part if called upon by new head coach Roy Hodgson.
He said: "It's not just about the 11 that start if we are going to go far in this competition.
"The boss has already said that. You have to be ready to come off the bench and play a part. He has made that clear to us."
Walcott is full of confidence after believing he produced some of the best form of his career during the past season with the Gunners.
He said: "It was important that I had no injuries last season which was one of the best I had for Arsenal considering the amount of games I had.
"I had a little hamstring injury at the start of this tournament but that is fine."
Rooney has had to sit out the opening two games against France and the Swedes after receiving a two-game ban for his red card against Montenegro in a qualifier in Podgorica in October.
Welbeck will happily welcome back his Manchester United team-mate even though he will be one of the players under threat of losing his place.
He said: "Make no mistake, the whole team is happy that Wazza will be available to play again.
"We all want want to play but it's only going to benefit us to have a player of his proven quality as part of the plans going forward in this tournament."