Hart's career appeared to be in limbo just over 12 months ago as it quickly became apparent Shay Given was the number one choice at Manchester City of then-manager Mark Hughes.
But a season-long loan spell at St Andrew's was just what Hart needed to kick start his career.
He was chosen as part of the Professional Footballers' Association Premier League team of the season and earned a place in the World Cup squad.
Hart had been confined to friendly internationals before Friday night's Euro 2012 qualifier with Bulgaria at Wembley.
But he produced several fine saves to almost certainly cement his spot for Tuesday's clash in Switzerland.
Hart said: "I can't stress enough how important that year was at Birmingham.
"If I'd been sitting on my backside last year and not playing, that would have done nothing for anyone.
"City wouldn't have got anything from that and I personally would not have got anything.
"I was very grateful to Alex McLeish (Birmingham manager) for giving me that opportunity.
"Just playing has really helped me grow as a keeper, not necessarily being better at doing certain things, but just being a keeper, someone's keeper and being part of a team."
Hart believes Birmingham's summer signing and England rival Ben Foster will also benefit from working with goalkeeping coach Dave Watson.
He said: "I can't speak any more highly of Dave Watson. I worked closely with him.
"Every day means the world to him football-wise and he is going to do the same with Ben.
"He will really push him. Ben is a great keeper and it will be great for him to be a number one and you have seen in his early performances that he is going to do well."
Hart has his feet on the ground despite his rapid rise and plays down the recent claims from England legend Gordon Banks that he is ready to step into his shoes.
He said: "I'd like to but they are massive shoes to step into. He's a man I look up to and respect massively.
"For him to even mention my name is a great honour.
"I'm just going to do my best for my club and country whenever I'm called upon, to try and move on and push forward.
"I'm just trying to enjoy my football, that's what I've always done.
"It was nice to get the opportunity in front of the home fans at Wembley.
"You don't really get much to do in these games because we tend to dominate at Wembley so it was nice to do my little bit.
"I just love playing. The opportunities that are coming at the moment are so exciting so I'm trying to embrace them and do the best I can."
Hart was full of praise for England's new-look defence of Michael Dawson and Phil Jagielka and, after the former was injured, Gary Cahill.
He said: "I thought they did brilliantly. I was gutted for Dawson when he got injured.
"I thought Jags was brilliant from the off. Cahill did great when he came on."
Hart knows England will have to be on song if they are to achieve a positive result against the Swiss.
He said: "England are a big scalp for people and look forward to playing us. They want to beat us.
"As a nation we have got to embrace that and really try to take it on.
"It's going to be an exciting game on Tuesday but different to Friday.
"We have to be solid, have got to work hard together and hopefully get the right result."