“I feel unhappy I am so sad. I lost the best friend I ever had,” wrote Kelly Osbourne alongside a broken heart emoji over a black background.

Hundreds of rock and heavy metal fans will gather together to pay tribute to Ozzy Osbourne in Birmingham on Saturday.

He became known as the Prince of Darkness and, relatedly, the godfather of heavy metal, which emerged as the name for the subgenre that flourished and then fractured in the wake of Black Sabbath’s su...