In one scene-stealing cameo from James Corden as an M&M-munching record executive, they’re asked where they come from.
Beverley Hills, they say. The estate, they add. The projects, they correct – too late.
“These are cornerstones of hip-hop,” says McAvoy. “That authenticity and that sense of place in the streets that made you.
“That is the lifeblood of rap music and hip-hop music, and they had to sacrifice that.
“But you have to accept that comes at a price.”
McAvoy, who has appeared in 30 films including Filth, Atonement, and X-Men, set the bar high for his cast – who had to act, rap, skateboard and perform at a specially arranged gig at Glasgow’s Barrowland for 2,000 extras.
“I needed them to be able to skateboard, beatbox, freestyle,” McAvoy said. “But I needed them to have chemistry.
“The film’s not about two individuals, it’s about a friendship.”