Bellingham became Birmingham City's youngest ever first-team player in August 2019, surpassing Trevor Francis' record of 16 years 139.
The Englishman's instant transition into senior was nothing short of phenomenal, drawing eyes to St. Andrew's from all over Europe.
He quickly cemented his place in the City starting line-up and would go on to make 44 total appearances in his debut season, which included four goals.
And Clark revealed the club had earmarked Bellingham's talent at the age of 9.
"They knew [about his talent] even then at the age of 9. My son was in the same group as his brother Jobe and he would come back and talk about Jude, and I used to go watch the academy almost every night. I'd see all the boys that were there."
But the midfielder had his eye on joining Borussia Dortmund, who eventually paid an initial fee of £25m.
The decision so far has proved to be a shrewd one as Bellingham has racked up 22 league appearances and eight Champions League appearances.
And Clark was effusive in his praise of the youngster, adding: "I knew about this boy and when you're talking about the whole package, here's a lad who is an unbelievable talent that is still a teenager, playing in Europe, playing international football, playing for one of the biggest clubs in Europe in Dortmund.
"He has taken it all in his stride. Jude has terrific character, brilliant lad, unbelievable mentality."
Such is Bellingham's talent that he was called up by England manager Gareth Southgate for the recent World Cup qualifiers, instead of playing for the U21s in the European Championships.
And Clark thinks a player like Bellingham can continue to thrive in the England set-up under Southgate.
"These players are getting nurtured by the current England manager because he's big into the young players, he doesn't seem to be bothered about a birth certificate, he just worries about how good the player is."