The present invention provides a method of drilling a hole in a workpiece in order to control breakthrough of the workpiece comprising the steps of : a) initiating contact between a drill bit of a drill unit and the workpiece; b) operating the drill unit to rotate the drill bit to drill the workpiece; c) during drilling of the workpiece measuring the force, F and torque, T, experienced by the drill bit; d) calculating a variable F', based on the measured force, F, representing the rate of change of F; e) calculating a variable, T' based on the measured torque, T, representing the rate of change of T; f ) calculating a variable F' ' representing the rate of change of F'; g) calculating a variable T ' ' representing the rate of change of T'; h) detecting the onset of breakout of the workpiece by use of the variables F', F' ', T' and T' '; i) thereby controlling the speed of rotation of the drill bit during breakthrough of the workpiece to control the degree of breakout of the drill bit from the workpiece. A drilling system is also disclosed.