The grime star was working with Ed Sheeran and the rap icon on ‘Take Me Back To London’, which featured on Sheeran’s No 6 Collaborations Project album.
Discussing the track on The Jonathan Ross Show, Stormzy explained how Jay-Z was originally set to appear on the hit too.
Stormzy explained: “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.We got into the studio and we were writing for this song and then he just stops the music and he said, ‘Tell me about London, I need some inspiration.'”
He then explained how he and his manager began telling Jay-Z about his home city, leading the pair to have “this powerful, beautiful, greatest conversation of my entire life”.
The pair discussed “black culture, community, music, his journey, my journey”.
Stormzy explained: “At the end he’s smiling, we were probably talking for an hour and he goes, ‘So what do you think of the song?’… I had verbal diarrhoea.
“I was like, ‘I love this song but you being on the song changes everything.’
“Take Me Back To London with me and Ed is one thing, but now that Jay-Z is on it… This is Jay-Z and Stormzy, what he means to culture, what I mean to culture… I said, ‘Is this the song?’ I didn’t think it was the song…”
Stormzy admitted Jay-Z was “super proud and super shocked and taken aback by the fact that this kid told him”.
He explained: “I felt proper bad because I was like, ‘You’re saying no to Jay-Z!’
“I was like, ‘If you didn’t ask me this, I would have just written my verse and we would have done it and I would have never questioned it but now that you’ve asked me, no.'”
“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.
“I don’t know why I’m saying this to you but this is not the song.'”
Despite turning down Jay-Z’s contribution, he described the encounter as the “greatest story” of his life and said Stormzy “fully understood”.
“We spoke and he made me feel [proud of what I did]. 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.”
Meanwhile, Stormzy recently attracted the praise of Labour leader Jeremy Corbyn after encouraging fans to vote and backing the MP’s leadership.
Next month, he will release his second album ‘Heavy Is The Head’.