As with the first two generations of the B-Class, the new model shares its underlying front-wheel drive platform with the A-Class, but with improved passenger comfort and load-lugging ability thanks to a taller roof line.
Every panel except the roof of this B-Class prototype is covered in camouflage, and there are also false body panels around the bonnet and front bumper.
With Mercedes-Benz preferring a strong family look for its ever-expanding range of models and variants, we expect the B-Class to borrow generously from the A-Class' design book.
Although our spy photography agency didn't manage to capture any photos of the B-Class' interior, it will likely feature the A-Class' dashboard design and overall aesthetic.
Mercedes-Benz has already revealed the next-generation A-Class' cabin. Thanks to two large connected screens, the new A-Class has a pleasingly minimalist interior.
Given this is the first sighting of the new B-Class, and the latest A-Class prototypes are running around with production lighting units and scant amounts of camouflage, we'd suggest the B-Class will debut at least six months after the covers are whipped off the new A-Class.
Reports indicate the fourth-generation A-Class will make its debut at the 2018 Geneva motor show, which takes place in March.