Eminem is one of those legacy rappers, much like Nas or Jay Z, whose co-sign will always hold weight​, even as hip-hop music evolves.

Although Kendrick Lamar has found himself now rising to such an iconic level, he once didn't have an easy time convincing Em that he was worthy of a mere compliment. In fact, according to English singer-songwriter Ed Sheeran, Eminem once thought that K. Dot was using a ghostwriter and chose to check him on it.

In a new interview on the Zach Sang​ S​how, the acclaimed musician recalls a specific story he was once told regarding a time Lamar found himself in the hot seat at Eminem's studio.

Around the 7:52 mark, Sheeran goes on to detail exactly what went down.

"I heard a very cool story about Eminem and Kendrick Lamar," he begins. "Eminem heard that Kendrick Lamar was the best rapper and he invited him to the studio to get him on a song. He arrived and Kendrick came with all his mates and Eminem said, 'I just want you in the studio, just you on your own and then my engineer is gonna come in and record you doing it, but your mates aren't allowed in.'"

At this point, many rappers, especially those new to the scene, would be internally freaking out. But of course, K. Dot played it cool and rose to the challenge. 

"Kendrick did it and wrote a sick verse. And then everyone came in to listen to it and Eminem said that he did it to test Kendrick 'cause he thought he had a ghostwriter," Sheeran recalls. "He then realized that he didn't, and then claimed he was the best, which is kinda cool I think."

Definitely an inspiring story and further testament to why we'​re so lucky to​ have a talent such as Kendrick Lamar in the game right now.

​Take a listen to Ed Sheeran discussing the moment Kendrick Lamar was personally tested by Eminem in the clip below.