A dark Bentley purrs down a West London side street and parks up. It’s far grander than the other cars lining the curb, you could lose yourself for hours in its glossy sheen. After a suitable pause, a figure in a black Nike tracksuit splashed with pink and green gets out, grabbing a Marks & Spencer bag from the boot.

Rapper Casyo Johnson, better known as Krept, heads inside the studio complex where he’s been working on new music with ...