A key witness to Sean 'Diddy' Combs' ongoing trial testified that Usher was in attendance at a star-studded dinner when the disgraced rap mogul assaulted Cassie Ventura in a restaurant.

The alleged altercation occurred in 2010 at a dinner where the singer joined Diddy and Cassie, alongside rapper Ne-Yo and Interscope Records co-founder Jimmy Iovine.

In testimony from Dawn Richards, a former member of girl group Danity Kane that was signed to Diddy's Bad Boy Records label, the court heard that Usher was at the dinner where a sickening attack on Cassie unfolded during an argument.

According to Richards, Diddy 'punched Cassie in the stomach' at the restaurant after the couple moved to a separate room.

She said she saw Cassie 'immediately bend over' after sustaining the blow, and said 'no one intervened' but did not clarify if the other celebrities in attendance saw the punch directly.