A valve train assembly for an internal combustion engine includes: a dual body rocker arm for controlling a valve of a cylinder, the rocker arm including a first body, a second body mounted for pivotal motion with respect to the first body, a first biasing means, and a latch pin moveable between a first position in which the latch pin latches the first body and the second body together and a second position in which the first body and the second body are un-latched to allow pivotal motion of the second body relative to the first body; and an actuator arrangement external to the dual body rocker arm and drivable by an actuation source, the actuator arrangement moving the latch pin from one of the first position and the second position to the other of the first position to the second position.