He has since progressed through their academy and made the bench in the Carabao Cup final win over Manchester City.
"He was already playing up and being highlighted as a serious player," Branston told LeicestershireLive.
"I was asked to work with the U13s and U12s, to work with the coaches, to give them an idea of what the next PDP (Player Development Plan) would look like as a coach, so I worked with his manager at the time.
"Stuart McClarty was asking me to work with him regarding what the potential stage would look like in a few more years for these boys. Trey was involved in that group over a period of time.
You're watching him train at the training ground and you're getting wind that he's a super talent. You're watching him play up and he's still flagging up. Then since I've left, he's stepped into the U16s and U18s and then watched him around the England set-up as well.
It leads to a tribunal because of discrepancies between an agreed price. They can't agree on the price of a youngster.
When you're talking about a super-talent like that, the standard remits that you get guidance on within the Football League and Premier League are blown out of the water because the kid's an uber talent."