The homage to the grime star's hometown topped the U.K. charts earlier this year, but he now reveals it almost featured the American rapper too.
Speaking to U.K. chat show host Jonathan Ross, Stormzy revealed that he vetoed Jay's contribution as he felt it took away from the British feel of the song.
The 26-year-old star says, "We were all in the studio writing, me, Ed Sheeran and Jay-Z. Before that I loved Take Me Back to London because I thought it was just going to be me and Ed and then Ed was like, 'Jay is getting on it.' It blew my mind. Jay-Z is my number one hero inspiration."
Stormzy and his manager spoke to Jay about London and black British culture with a view to him cutting a verse, but then the U.K. hip-hop star had second thoughts.
"I was like, 'I know how it goes, Mr Z. You are the most brilliant, busy man and I will probably never get this opportunity ever again but hand on my heart, I don't think this is the right song for us'," he tells Jonathan. " 'I don't know why I'm saying this to you but this is not the song.' "
Describing the encounter as the "greatest story" of his life, Stormzy said the U.S. superstar "fully understood" his decision, and later praised him for standing up for his art.
"We spoke and he made me feel (proud of what I did)," the musician says. "I left there thinking (I was an idiot) but then I had the honour of seeing him again and having the conversation and he let me know to my face that what I did (was courageous). He couldn't believe that I did it."
Stormzy's chat with Jonathan will air on U.K. network ITV on Saturday, November 30. The rapper also announced a 55 date world tour on Friday, that will take in Europe, Asia, Australia and New Zealand, and North America.