Is it mandatory to warn other road users that a manoeuvre is going to be performed?

Manoeuvres may alter the normal driving conditions of other vehicles, and their drivers may be affected or taken by surprise. Therefore, a driver who intends to perform a manoeuvre must obligatorily signal their intention to the rest of the road users with sufficient advance notice. We will use the vehicle's lighting systems or, failing that, the arm to signal it. Signalling a manoeuvre does not grant priority to carry it out.