Hydraulically controlled disc brake, including a hydraulically actuated parking brake, which includes: - a brake caliper which includes a casing in which a primary hydraulic cavity is formed, axially open towards the front, - a primary piston which is mounted to slide axially, in a sealed manner, in the primary hydraulic cavity of the casing, in which it axially defines a primary hydraulic chamber and which is capable of cooperating with an associated disc-brake pad in order to exert a primary force on the latter, with axial thrust, from rear to front, when the primary hydraulic chamber is supplied with pressurised fluid; - a piston rod which is axially movable with the primary piston relative to the casing, which is rotationally immobilised relative to the casing, and which includes a threaded section; - a wheel, for axially locking the piston rod, which is mounted screwed, in a reversible manner, on the threaded section of the piston rod so as to be axially movable relative to the piston rod, towards the rear by screwing or towards the front by unscrewing; - a controlled electric motor capable of rotating the locking wheel; - a transverse axial stop plate which is axially fixed relative to the casing and which includes a front transverse stop face, and in that the locking wheel is axially movable relative to the piston rod, between a front position and a rear stop position in which the locking wheel axially bears, towards the rear, against said front transverse stop face; and - a secondary hydraulic cavity, a secondary piston which is mounted to slide axially, in a sealed manner, in the secondary hydraulic cavity in which it defines a secondary hydraulic chamber and which is capable of cooperating with the piston rod in order to exert a secondary axial thrust force on the latter, from rear to front, when the secondary hydraulic chamber is supplied with pressurised fluid, in order to apply, to the primary piston, an additional hydraulic force for actuating the parking-brake brake; wherein the primary hydraulic cavity is axially defined, towards the rear, by a transverse bottom wall through which the piston rod passes in a sealed manner, and in that the threaded section, the locking wheel and the transverse stop plate are axially arranged at the rear of the transverse bottom wall, outside the primary hydraulic chamber, wherein the locking wheel is rotated by the electric motor by means of a non-reversible mechanical transmission (176, 144) in such a way that the locking wheel is rotationally immobilised by the mechanical transmission (176, 144) when an output shaft of the electric motor is not rotated, characterised in that the secondary hydraulic cavity and the secondary piston are arranged axially behind the transverse stop plate, outside the primary hydraulic chamber. - a brake caliper which includes a casing in which a primary hydraulic cavity is formed, axially open towards the front, - a primary piston which is mounted to slide axially, in a sealed manner, in the primary hydraulic cavity of the casing, in which it axially defines a primary hydraulic chamber and which is capable of cooperating with an associated disc-brake pad in order to exert a primary force on the latter, with axial thrust, from rear to front, when the primary hydraulic chamber is supplied with pressurised fluid; - a piston rod which is axially movable with the primary piston relative to the casing, which is rotationally immobilised relative to the casing, and which includes a threaded section; - a wheel, for axially locking the piston rod, which is mounted screwed, in a reversible manner, on the threaded section of the piston rod so as to be axially movable relative to the piston rod, towards the rear by screwing or towards the front by unscrewing; - a controlled electric motor capable of rotating the locking wheel; - a transverse axial stop plate which is axially fixed relative to the casing and which includes a front transverse stop face, and in that the locking wheel is axially movable relative to the piston rod, between a front position and a rear stop position in which the locking wheel axially bears, towards the rear, against said front transverse stop face; and - a secondary hydraulic cavity, a secondary piston which is mounted to slide axially, in a sealed manner, in the secondary hydraulic cavity in which it defines a secondary hydraulic chamber and which is capable of cooperating with the piston rod in order to exert a secondary axial thrust force on the latter, from rear to front, when the secondary hydraulic chamber is supplied with pressurised fluid, in order to apply, to the primary piston, an additional hydraulic force for actuating the parking-brake brake;