Cadet has died in a car crash on the way to a gig in Staffordshire.
The rapper’s family shared the news on his official Instagram account.
“We the family of Blaine Cameron Johnson otherwise known as Cadet (Underrated Legend) would like to share the sad news that during the early hours of 9th February 2019 he passed away.”
In a statement to Radio 1 Newsbeat, his management said the 28-year-old was a passenger in a taxi.
Cadet’s cousin Krept led the tributes online, saying he was “heartbroken”.
Staffordshire Police confirmed Cadet died in the crash in Betley in the early hours of Saturday morning.
In a statement, the force said: “Blaine Cameron Johnson, 28, of London, died after the Toyota Prius he was travelling in was involved in a collision with a Vauxhall Combo van at 1.30am.
“He was pronounced dead at the scene.”
A previous statement said that the drivers of both vehicles were taken to hospital with serious injuries and three others were also being treated in hospital.
Cadet was on his way to Keele University where he was due to perform.
This year was set to be massive for Cadet
by Nick Bright, Radio 1Xtra DJ
For us at 1Xtra he was a huge artist.
Lots of his tracks were on the playlist last year, and even as we speak at the moment one of them is on the A-list, so it’s one of the tunes that gets played the most.
To see this happen to an artist just as he’s about to break through is a really sad thing.
He’s consistently being putting out music. The Commitment and the Commitment 2 are probably two of the most known pieces of work he’d put out.
He got so much recognition from those projects alone and lots more people have been paying attention to his music.
He’s worked with Krept and Konan, two of the biggest rappers in the UK and Deno Driz on Advice.
It’s quite a small scene so when something like this happens everybody within this industry knows it’s happened.
There’s no doubt in my mind that he would have been playing at so many different places this summer because he’s got so many big songs out at the moment and loads in the pipeline.
Cadet regularly appeared on BBC Radio 1Xtra performing at MistaJam’s Christmas Party last year.
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Cadet was due to perform at Wireless in July.
In a statement on the festival’s website, it said: “Our thoughts and prayers go out to the family, friends and fans, of Cadet.
“Such sad news.
“We’ll be keeping his Wireless performance as a time to reflect on the memory of Blaine.”