Hain was born in Hong Kong to English parents but was raised on the Gold Coast and represented Queensland at under-17 and under-19 level.
Despite now revealing he harboured intentions of forging a career in England since the age of 14, he was selected and played for the Australia Under-19 team, including at the 2012 Under-19 World Cup, where the team finished second.
Quick Single: Rogers' ton not enough for victory
This week Hain became the youngest player to score a first-class century for Warwickshire when he tallied a composed 134 against Northamptonshire. However after the match, he turned his back on the Baggy Green.
"I'm a fair-dinkum pom, to say the least," Hain said.
"The Australia U19 thing happened, but I was always set to play in England ever since I was 14," he told ESPN.
Hain's remarks come a week after Sydney-born and raised Sam Robson made his Test debut for England, where he scored 1 and 19 as Sri Lanka battled bravely to hold on for a draw at Lord's.
The now 18-year-old Hain beat the previous record for Warwickshire's youngest century-maker, set by England international Ian Bell who this week plays his 100th Test, by 173 days.
Hain’s ton lifted Warwickshire to a big victory, the West Midlands side orchestrating a monumental Northamptonshire collapse to win by an innings and 105 runs.
Hain made his Australia Under-19 debut in Townsville in April 2012 against England Under-19s during a quad-series ahead of the 2012 ICC Under-19 World Cup in his home state of Queensland.
Aged just 16, Hain scored 43 runs in two appearances in the World Cup group stages, key innings that helped Australia to victory on both occasions, before more experienced players were selected for the tournament's latter stages.
Hain has drawn comparisons in technique and temperament to former England No.3 Jonathan Trott, who sensationally quit England's disastrous Ashes tour last summer to return home with mental health problems.
"When I first heard it (the comparison to Trott) I was quite chuffed," Hain told the Birmingham Mail newspaper.
"If I can have half the career he has got then I’ll be happy."