The jubilant grandfather of young football star Harry Wilson is set to bank £125,000 after betting the teenager would play for Wales – back when Harry was a toddler.

The 16-year-old Liverpool academy star made his international debut last night – scoring a big win for his grandfather the moment he came on as a substitute.

Peter Edwards, 62, walked into a William Hill betting shop in Wrexham in 2000 and bet £50 on the teenager one day playing for Wales, at odds of 2,500-1.

The teenager scored one for the record books himself during last night's World Cup qualifier against Belgium, becoming the youngest player to represent Wales.

But one life-changing moment instantly gave rise to another when Edwards decided he would retire with immediate effect on the proceeds of his win.

He made the decision in his caravan in Buckingham, where he was working, nervously watching the international clash on his iPad.

The electrical contractor of Corwen, Clwyd, North Wales, works away from home most of the year, spending one weekend a fortnight with wife Dorothy, 58.

"She is over the moon. I retired immediately. I told my manager yesterday that if Harry plays I wouldn't be coming back," he said.

"I've retired one year early. I have come home now and will not be going back. Not bad for a daft bet."

He said he put on the original bet on a whim after seeing how Harry liked playing with a football even as a toddler.

"He used to chase the ball around the front room on his hands and knees even before he could walk, that's what gave me the idea. But I hoped the bet would come up."

He said after Harry enrolled in the Liverpool FC academy his skills quickly developed and he returned to William Hill in the hope of placing a second bet.

"Harry was about 12 then. But they turned me down and said I already had a substantial bet with them. But they threw in England as a gesture of goodwill."

It meant even if the teenager had opted to play for England, something he could have done because his grandmother was born in Chester, the payout would have been safe.

Harry himself will also benefit from the win, which Edwards said would ensure regular lengthy journeys to and from Liverpool would be made easier.

He said that as a teenage player with the academy his earnings were still modest and travel costs could be high.

"This means I will be able to help Harry out. You can be quite sure that he will get a share of it," he said.

• This article was amended on 17 October 2013. The original version gave Harry Wilson's age at the time of the bet as 18 months. In fact it was made in 2000, when he was slightly older.