Flyweight Andrew Selby has targeted an Olympic medal after securing his place at the 2012 London Games.
Selby secured his Team GB place after Khalid Yafai failed to make the weight for the second bout of their box-off.
Yafai had lost his opening bout against Selby on Friday night, as the Welshman outpointed him 26 points to 12.
"It still hasn't hit me yet, I'm over the moon and it's going to be a great experience to go to the Olympics and fight for my country," Selby said.
"We both had to weigh-in again and my opponent failed to make the weight, and he had a bad hand as well, so I automatically go through.
"I felt I did enough to go anyway and then I beat him by a big margin [on Friday] so I think I still proved a point.
"It boosted my confidence right up and I thought I'd win today. It's a bit of a shame we didn't have to fight but I thought I should have been going anyway."
Barry-born Selby, 22, has come back strongly after suffering a slump in his early amateur career and became Wales' first European amateur champion in 86 years when he beat former three-time champion Georgy Balakshin.
He followed that up with a silver medal at the World Amateur Championships in Baku and will now get the opportunity to go one better and claim gold in 2012.
"I wasn't doing the weights so well because I had to move down to 52kg from 54kg and I was struggling for a year, and that's when I performed badly," Selby said.
"But I just had to wake myself up, eat the right foods, be dedicated and train a little bit harder - and that's where it's got me now."
Selby will now join Welsh compatriot Fred Evans in the British team, who had already secured his place in the 69kg division.
"It's great, Fred's a really good friend as well so it'll be good to support each other and we shouls have a lot of family going to watch us and support us," Selby added.
"I just want to do the best for my country and hopefully bring back home a medal."
Speaking about his failure to make the weight, Yafai explained: "We normally have an optimal boxing weight but I knew I had to be strong for this fight and put an extra bit of weight on for an extra bit of power.
"I hurt my hand in the [first] fight and my hand swelled up and I had a bruised knuckle. I spent a lot of time getting that seen to by doctors and physios and by the time I got back to the hotel I was 1.7kg over.
"I tried to get most of it off last night and I did, and then I had 0.9 to get off this morning. We did train this morning for an hour and a half, we had two attempts this morning but the scales closed at half past nine and I lost out by 300 grams.
"I just want to say well done to Andrew, I wish him all the best and I hope he gets a gold for Great Britain."